LIGHT (SPM)

LIGHT (Overview): Form 4 Chapter 5

Reflection in Mirrors; Refraction through Lenses, Etc.

1.    Reflection of Light

a.       Law of Reflection

b.      Image formed by reflection in

                                                               i.      plane mirror; characteristics of image and applications

                                                             ii.      convex mirror, characteristics of image and applications

                                                            iii.      concave mirror, characteristics of image and applications

c.       Ray diagrams for reflection

2 .   Refraction of Light

a.       Law of refraction

b.      Refractive index, n

c.       Natural phenomena due to refraction

d.      Total internal reflection

                                                               i.      Internal reflection

                                                             ii.      Total internal reflection

                                                            iii.      Critical angle

                                                           iv.      Natural phenomena due to total internal reflection

                                                             v.      Applications of total internal reflection

1.      Prism periscope

2.      Prism binoculars

3.      Optical fibre

4.      Cutting of diamonds

3.    Lenses

a.       Convex lenses and Concave lenses

b.      Terminologies and Lens Formula

                                                               i.      Focal length, f.

                                                             ii.      Focal point, F.

                                                            iii.      Object distance, u

                                                           iv.      Image distance, v.

                                                             v.      Magnification, m = v/u

                                                           vi.      Power of lenses, P = 1/f

                                                          vii.      Lens formula: 1/f = 1/u + 1/v

c.       Uses of lenses in optical devices

                                                               i.      Magnifying glass

                                                             ii.      Compound microscope

                                                            iii.      Astronomical telescope

                                                           iv.      Camera

                                                             v.      Slide projector

                                                           vi.      Photocopier

                                                          vii.      Short-sighted spectacles

                                                        viii.      Long-sighted spectacles

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Forces and Motion - Chapter Review Questions (SPM Fm 4 Chapter 2)

Updated on 21/7/2013...more updates to follow thereafter...

A)  Linear Motion, Ticker Tape, Distance, Displacement, Speed, Velocity and Acceleration

1.      2012 P1 Q6 at pg 332: Diagram shows a man walks from O: 2m towards west and then (2 + 7)m towards east. What is the displacement of the man? Answer: C, 7 m to the east (because displacement is the shortest straight line distance two reference points which are, in this case, the starting point O and the final point B. hence taking towards west or A as negative and towards east or B as positive, we have: -2m + (2 + 7)m = 7m i.e. displacement 7m to the right)

2.      2012 P1 Q11 at pg 334: Which ticker tape shows movement with uniform velocity and then deceleration? Answer: Tape in B (because the distance between initial intervals is the same meaning uniform velocity and then the distance get smaller and even smaller for later intervals, implying decreasing speed over time i.e. deceleration)

B)  Motion Graphs

1.      2012 P1 Q9 at pg 333: Diagram shows the velocity-time graph of a bus with passengers on board. The driver applies brakes after 10 minutes.  The graph shows an upward climbing straight line from the origin to velocity 6 m/s at time 10 s, then followed by a downward inclined straight line ending at velocity 0 at time 12 s. Q: What is the velocity of the passengers immediately after the brake is applied? Answer: C (because inertia will cause the passengers to move at the velocity just before the brake is applied i.e. at 6 m/s hence C)

2.      2012 P1 Q10 at pg 333: Diagram shows a mango falling – Q: Which acceleration-time graph represents the motion of the mango? Answer: B (for short distance fall, air resistance (drag) doesn’t lower the mango’s acceleration, g, much – so, the seemingly horizontal straight line in B represents its seemingly constant acceleration.)

C)  Inertia

1.      2012 P1 Q5 at pg 332: Shown 4 events / phenomena: A, an archer shooting an arrow; B a boy floating on a float; C, a ping pong ball floating under a tap with water flowing downwards around the ball; and D, shaking tomato sauce out of a tomato sauce bottle. Q: Which phenomenon shows the effect of inertia? Answer: D (because inertia will cause the sauce to move out at the speed just before the bottle’s movement is abruptly stopped)

D)  Momentum – Elastic and Inelastic Collisions; Explosions

1.      2012 P1 Q7 at pg 332: Question shows a trolley with mass 1.5 kg and velocity 2 ms^-2 collides with a stationary trolley of mass 1.0 kg. After the collision, both trolleys move together. Q: What is the velocity of both trolleys after the collsion? The collision is inelastic (trolleys stick together after collision) BUT the nature of the collision – whether elastic or inelastic- is immaterial because Law of Conservation of Momentum applies in either cases. The velocity after collision can found by equating momentum before collision to momentum after collision. Thus, m₁v₁ = (m₁ + m₂)v and v = 3/2.5 = 1.2 m/s – hence C)

2.      2012 P2 Secion A Q5 at pg 350~352 (8 marks): Collision and Conservation of Momentum - Diagram shows collision of bowling ball and bowling pin – Table shows momentum before and after collisions for ball and pin – Q:

·        What is the meaning of momentum?

·        Based on diagram and table, determine total momentum of ball and pin before and after collision (simple adding of values given in table)

·        Compared added values (same before and after collision)

·        Based on aforesaid comparison,  state a conclusion about total momentum (conserved or remained the same before and after collision)

·        Name the physics principle involved in foregoing conclusion (Law of conservation of momentum)

·        State 1 condition needed for the foregoing physics principle to apply (no other external forces act on  the bowling ball and pin)

·        Given: after collision, total kinetic energy of the ball and pin decreases – state the type of collision involved (inelastic collision)

3.      2011 P1 Q5 at pg 280:

Diagram shows 3 identical coins at rest on a horizontal surface. Q: What happens when 1 coin collides into the 2 coins which abut each other? (Ans B – situation of approximate elastic collision – much like in the case of Newton’s cradle – momentum and kinetic energy conserved)

E)   Effects of a Force – Balanced and Unbalanced Force

·        Newton’s 1st Law of Motion:

o   An object, if at rest, tends to remain at rest and if in motion, tends to move at the same speed in a straight line unless there a net force acting on it. Therefore,

§  A net force is needed to change velocity i.e. magnitude and/or direction

§  A net force changes momentum and causes impulse

§  A net force changes an object’s state of motion i.e. its state of equilibrium – static or dynamic

o   Any object with mass has inertia (covered in a separate segment) i.e. the natural resistance to change its current state of motion

·        Newton 2nd Law of Motion

o   An object subjected to a net force always experiences an acceleration (or rate of change in velocity) which is:

§  directly proportional to the net force

§  inversely proportional to its mass

§  summarised as: F = ma or a = F/m = (mv – mu)/t divided by m

1.      2012 P1 Q8 at pg 333: Diagram shows a woman pushing a trolley with force F. Q: Which of the 4 option shows the total downward force? Answer: A (because the downward force comprises the downward component of the push F (F_y) the weight of the trolley (mg) – thus A: F_y + mg)  

2.      2011 P1 Q6 at pg 281: Diagram shows a boy pulling a block on a rough surface with force F. Q: Diagram in which options shows action of forces acting on the block. (Answer D – My comments: The boy’s upward diagonal pulling force F tends to do 2 things: 1) the horizontal component F_h triggers “Friction” - if F_h = Friction, the block remains at it prevailing state of motion (not given) – either at rest or motion with uniform velocity; and, 2) the vertical component F_v tends to lift the block up against the downward gravitational force on the block – with the boy pulling, the “Normal reaction’ is lower than that without the boy pulling the block. F_v  + Normal reaction = Weight of the block. When F_v = 0 (boy not pulling), Normal reaction = Weight of the block)

F)   Impulse and Impulsive Force

1.      2012 P2 Section C Q11 a) and b) at pg 363~366 (5 marks):

·        Diagram shows golfer continues swing after golf ball is hit in what is called ‘follow through’

a)      What is the meaning impulse? (1 mark)

Answer: Impulse is the change in momentum (= mv – mu)

b)      Explain how follow through can increase impulse? (4 marks)

Answer: Follow through can increase impulse because:

§  Impulse = Ft = mv - mu.

§  With follow through, the time, t, that the swing force F acts on the golf ball increases;

§  which means Ft increases or the change in momentum (mv – mu) increases. ;

§  This results higher impulse - that is higher final velocity (v)  for the golf ball since initial momentum mu of the golf ball is zero and mass of the ball m is constant.

2.      2011 P1 Q4 at pg 280:

Diagram shows a long-jumper bends his legs upon landing. Q: Bending his legs to reduce what? A. Impulse B. Impulsive force C. Velocity D. Time of impact? Answer: B (Because bending his legs increases the time of impact thereby reducing the impulsive force on his legs)

G)  Force and Motion Affect Safety Features in Vehicles

Questions coming up soon…check out the blog

H)  Gravity

I)     Forces in Equilibrium

1.      2012 P1 Q 4 at pg 332: Diagram shows 4 forces acting on a stationary object – Q: Which statement about the forces is correct? Answer: C (because when an object is stationary, the 4 forces are in equilibrium, meaning the vertical opposite forces F₁ = F₂ (not a given option) and the horizontal opposite forces F₃ = F₄ (option C). – hence C)

J)    Work, Energy, Power and Efficiency

1.      2012 P2 Sec C Q11 d) at pg 365~366 (5 marks): Diagram shows a 60-kg man sliding down a water slide from top point A to bottom point B. Q:

a.       energy transformation – potential to kinetic;

b.      calculation of gravitational potential energy;

c.       calculation of speed ignoring friction.

(Note: To find the speed, I suggest you use the Law of conservation of energy: GPE (mgh) = KE (1/2mv²); If you use the equation of linear motion (v² = u² + 2as), you appear to suggest that all the GPE is converted into vertically downward component speed v? If so, where does the energy that causes horizontal displacement come from - if not from the GPE? The v will obviously not be in the same direction as the direction of a i.e. g, acceleration due to gravity)

K) Importance of Maximising Efficiency of Devices

 Q & A coming up soon...

L)   Elasticity

....Lots of Q & A coming up soon...

A's for Physics, Chemistry and ALL Subjects in SPM 2012

They were my 1st batch of SPM tuition students from SMK (Girls) Sri Aman and they excelled!

Congrats to ALL 8 of them as  follows:

FULL A's:
1. Huda Liyana (9As - physics A+)
2. Adina Bt. Ahmad Bakhtiar (10As - Top in Maths)
3. Hana Suhaila (10As)
4. Siti Sara (10As)
5. Ksherah (10As)
6. Niraanjana Sunathan (9As)

They all scored FULL A's (A's for ALL subjects) in SPM 2012; and, a few scored A+ for PHYSICS. The sweetest thing is: They all took physics tuition from me and a few took Chemistry too. Huda called and sms the same moment she got the good news - could imagine she must be jumping with joys! Her Mom too sms a nice "Thank You" note.
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It could have been 8 scoring FULL A's if not because two of them missed full A's by the whisker.

Missed Full A's By the Whisker:

7. Yasshene Ann (8As)
8. Uma Priya (7As)

Full A's from SMK Taman SEA
1) Manoj (Full A's with A+ for Physics n Chemistry)
2) Huey Mei (Except Moral B+, full A's including Physics, Chemistry, Add-Maths, Mod Maths)
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Simple Kinetic Molecular Model of Matter

IGCSE Cambridge Syllabus Area 2.1

.1       States of Matter – Solids, Liquids and Gases

State the distinguishing properties of solids,
liquids and gases (in terms of simple kinetic molecular model of matter)

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Matter can be in 3 possible states: solids, liquids or gaseous states.

In solids: the constituent particles are closely packed in regular / lattice arrangement and vibrating in fixed position - the higher the temperature, the more vigorous the vibration and vice versa. Solids have fixed volumes and fixed shapes

In liquids: the constituent particles are no longer in  regular arrangement - they are constantly translating past each other. Liquids have fixed volume and take the same of their containers.

In gases: the constituent particles are far apart and they move randomly in straight lines in all direction, colliding with each other and with the walls of their containers in the process. The higher the temperature, the higher the kinetic energy of the particles.


.2 Molecular Model (of Matter)

1.    Matter is made up of tiny particles which can be: mono-atomic (as in noble gases like helium, He), molecular (as in water, H₂O; oxygen, O₂; nitrogen, N_2;  etc) or (as in common salt, sodium chloride, NaCl). The atoms that make up the particles of each substance are unique in terms of: the type of atoms and the ratio they bear to each other - eg. the particles of water are made up of hydrogen and oxygen atoms in the ration of 2:1 whatever the states (solid, liquid or gaseous) that water is in.

2.    The particles of matter are too tiny to be seen with our naked eyes - however, they can only be seen with the aid of instruments such as electron microscope. Nevertheless, their random nature of motion can be indirectly seen with normal microscope: When large smoke particles are in suspension in air in a glass cell or smoke chamber or larger pollen grains are in suspension in liquid water and seen through normal microscope, these larger particles can be seen as moving around haphazardly - in what is known as Brownian motion - due to random bombardments by the tiny but fast-moving energetic particles of the air or liquid water, whichever is applicable. 

3.    Depending on its temperature, a substance can exist either in solid, liquid and/or gaseous states. In solid state, its temperature is lower than that in liquid state; and in gaseous state, its temperature is even higher.

4.    The melting or freezing point of a substance refers to the temperature (under normal atmospheric pressure) below which the substance exists as a solid; and at which, the substance changes state from solid to liquid or vice versa. This temperature is a unique physical property of the substance. For pure water, it is 0^o C or 273^o K and is also referred to as the ice point.

5.    The boiling or condensation point of a substance refers to the temperature below which the substance exists as a liquid or solid; and at which the substances changes state from liquid to gaseous state or vice versa. Again, this temperature is unique to each substance. For pure water, this temperature is 100^o C or 373^o K and is also known as the steam point.

6.    The distinguishing properties of a substance in solid, liquid or gaseous states may be described in terms of the following characteristics of its constituent particles:

i)      distance between them – closely-packed, further apart or furthest apart;

ii)    their arrangement - in fixed position, in loose-attachment or without any attachment;

iii)   their movement – to and fro vibrations about fixed position; moving and changing position while loosely attached to one another; or dashing randomly and independently from one another;

iv)  forces of attraction and repulsion between them – strongest to hold the particles in fixed positions, present to hold them loosely together or negligible.

7.    Hence, in terms of kinetic molecular model of matter, a substance in solid, liquid or gaseous state may be described as follows (syllabus area 2.1 (b)):

a.       In Solid State:

Its constituent particles are closely-packed, vibrating to and fro in fixed positions experiencing the strongest forces of attraction and repulsion between them much like having springs holding them together in fixed shape and volume.

Temperature and Expansion: When the temperature of the solid rises (without exceeding its melting point), the vibrations become more vigorous resulting in the distance between neighbouring particles getting bigger and hence the expansion of the solid.

b.      In Liquid State:

The constituent particles are further apart and in loose attachments, vibrating vigourously and changing positions and slipping past each other easily – resulting liquid having fixed volume with shape that varies with the shape of its container.

Convection and Expansion: When the temperature of the liquid rises (without exceeding its boiling point), the vibrations and movement of the particles become even more vigorous resulting in the distance between neighbouring particles getting bigger - hence, the hotter part of the liquid becomes less dense and the particles rise as in convection; and, hotter liquid expands.

Evaporation (syllabus area 2.1 (c)):

Energetic liquid particles at the surface of the liquid, though still below its boiling point, may have enough kinetic energy to escape from the main body of the liquid in what is known as evaporation.

Evaporation results in cooling because the evaporated particles leave with higher energy level leaving behind particles with lower thermal energy.

Factors influencing rate of evaporation: The higher the room temperature, the bigger the surface area for evaporation, the higher the movement of air (draught) and the lower the humidity of the surrounding, the higher the rate of evaporation.

Evaporation, unlike boiling that only occurs at boiling point, can occur at any temperature below boiling point as long as the surface particles have enough energy to break away from the main body of the liquid.

c.       In Gaseous State:

The constituent particles are furthest apart (least dense of all), no longer experiencing any significant force of attraction and repulsion between them and dashing around at high speed (about 500 m/s for air molecules at 0^o C), randomly and independently of one another in all directions. The higher the temperature of gas particles, the faster and more vigourous the random motion of the particles and the higher the force and rate of bombardment on the inner walls of its container and hence, the higher the gas pressure exerted. 

Brownian Motion (in gas):

When randomly-moving gas particles collide with other more massive particles such as smoke particles, they have enough energy to exert a net force on the more massive particles in what is seen as Brownian motion – the random bombardments of massive particles by high-energy tiny particles.

Pressure Changes in Gas (syllabus area 2.1 (d)):

When gas particles collide with the internal walls of its container, the particles exert a force and therefore a pressure on the inner walls of its container.

At constant temperature, the pressure exerted by a gas is directly proportional to its density. The higher its density ρ, the higher the pressure exerted P due to the higher rate of collisions of the particles on the inner walls of its container:

Thus, P α ρ    ⇔ P α mass (m)/volume (V) ≡ P α m/V

Hence,

·        when mass m increases (such as by pumping in more air into a tyre) with temperature and volume remaining constant, pressure P increases because density ρ of the gas has increased.

Thus, P₁/m₁ = P₂/m₂  = constant

·        when volume V decreases (such as by squeezing a balloon) with temperature and mass remaining constant, pressure P also increases because lower volume means greater density ρ.

Thus, P₁V₁ = P₂V₂ = constant (Boyle’s Law)

At constant volume, the pressure exerted by a gas is directly proportional to its temperature. The higher the temperature, the higher the pressure exerted because at higher temperature, the gas particles hit the inner walls of its container at higher frequency and with greater force.

Thus, P α T ⇔ P₁/T₁ = P₂/T₂ = constant (Pressure Law)

Thermal Physics

IGCSE Cambridge Syllabus (2020-2021) Area 2 on 'Thermal Physics'

Scope:

2.1 Simple Kinetic Molecular Model of Matter

.1 States of Matter

.2 Molecular Model (of Matter)

.3 Evaporation

.4 Pressure Changes (in Gases)

2.2 Thermal Properties and Temperature

.1 Thermal Expansion (and Contraction) of Solids, Liquids and Gases

.2 Measurement of Temperature

.3 Thermal Capacity - Heat Capacity (and Specific Heat Capacity)

.4 Melting and Boiling

2.3 Thermal Processes

.1 Conduction

.2 Convection

.3 Radiation

.4 Consequences of Heat Transfer

Chapter Review Questions: "Intro to Physics" - Form 4 Chapter 1

A)  Base Quantity and Derived Quantity

1.    What is a base quantity? Name 5 base quantities.

2.    Define derived quantity. And, state 5 derived quantities.

3.    State two main advantages of standardisation of all units of measurement for physical quantities.

4.    Give the name and symbol of the SI unit of measurement for each of the following physical quantities:

a.       Length

b.      Mass

c.       Time

d.      Temperature

e.       Current

f.        Force

g.       Energy

h.       Power

5.    Some derived quantities have been given special names by SI (International System of Units). State these derived quantities (that you know of) and their special names.

B)  Standard Form / Scientific Notation / Prefixes

6.    Express each the following physical quantities in its SI unit and in scientific notation to 3 significant figures:

a.    Acceleration due to gravity, g = 9.783 ms^-2

b.    Speed of light in vacuum, c = 298,000 kms^-1

c.    Length of an onion cell, L = 0.000 028 m

d.    Charge of an electron = -1.6 x 10^-7 pC (pico coulombs)

7.    For each of the following symbol of prefixes, state its name and its numerical value in index form (i.e. in power or exponential form):

a.    da

b.    h

c.    k

d.    M

e.    G

f.      T

g.    d

h.    c

i.      m

j.      µ

k.    n

l.      p

8.    Identify the largest and the smallest measurements from the following values:

A.     3.14 x 10³ km

B.     3.14 x 10⁸ nm

C.     3.14 x 10¹⁰ µm

D.     3.14 x 10^-2 cm

9.    Convert:

a.       Density of sea water from 1.05 x 10³ kg m^-3 to g cm^-3

b.      Velocity of cyclist from 5.6 m s^-1 to km h^-1

c.       Radio frequency from 102.3 MHz to Hz

d.      470 pF to F in standard form to 3 significant figures

e.       0.0006 Gm to Mm

f.        26 µm to mm

C)  Scalar Quantity and Vector Quantity

10.    State the main difference between a scalar quantity and a vector quantity.

11.    An object moves 40 km on a bearing of 090o from O to A in 20 minutes; it then immediately moves north 30 km also in 20 minutes to B. Find:

a.       The total distance travelled by the object from O to B

b.      The final displacement of the object in moving from O to B in terms of both magnitude and bearing from O.

c.       For the whole journey from O to B:

                                                               i.      The object’s average speed

                                                             ii.      The object’s average velocity

12.    Is pressure a scalar or vector quantity? Name 5 scalar quantities.

13.    Name 5 vector quantities and state their respective SI units of measurement.

D)    Measurements in Science

14.     All measurements in science are Man’s attempts to make an acceptable estimate of the true and actual value of a physical quantity – True or False?

15.    The difference between the true and actual value of a physical quantity and the value obtained in a measurement is known as ________________.

16.    There are two main types of errors. State them, describe their differences and how each type of error may be minimised or avoided – give examples where appropriate.

17.    Attempts the following past year SPM questions:

a.         2007 P1 Q3 pg. 92 - Which balance is more sensitive?

b.         2011 P1 Q2 at pg. 280 on sensitivity in measurement

c.         2005 P1 Q2 Pg 3 on consistency and precision in measurement 

d.         2008 P1 Q2 Pg. 140 – consistency and precision

e.         2011 P1 Q1 at pg. 280 – on use of vernier calipers

f.           2005 Paper 1 Q1 at Pg 3 – on use of micrometer srew gauge

g.         2010 Paper 2 Q1 at Pg. 246 – on use of stopwatch to measure 20 oscillations of pendulum

h.    2005 P2 Q1 Pg. 16 – on use of ammeter, anti-parallax mirror, etc.

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