WAEC Physics Answers 2022 Questions.
PAPER 2 [Essay]
Read Instructions.
Write your answers on the answer booklet provided.
1. Explain why mercury does not wet glass while water does.
ANS: Mercury does not wet glass because (force of) cohesion/attraction of mercury molecules is greater than (force of) adhesion/attraction between glass and mercury molecules.
Water wets glass because (force of) adhesion/attraction between glass and water molecules is greater than (force of) cohesion/attraction of water molecules
PAPER 2 [Essay]
Read Instructions.
Write your answers on the answer booklet provided.
1. Explain why mercury does not wet glass while water does.
ANS: Mercury does not wet glass because (force of) cohesion/attraction of mercury molecules is greater than (force of) adhesion/attraction between glass and mercury molecules.
Water wets glass because (force of) adhesion/attraction between glass and water molecules is greater than (force of) cohesion/attraction of water molecules
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(a) tate Faraday’s second law of electrolysis.
(b) An electric charge of 9.6 x 104 C liberates 1 mole of substance containing 6.0 x 1023 atoms. Determine the value of the electronic charge.
ANS: (a) If the same quantity of electricity is passed through different voltameters/electrolytes connected in series the masses of the substances liberated/deposited during electrolysis is (directly) proportional to their chemical equivalents.
(b) Let e represent the electronic charge.
e = Faraday’s constant
Avogadro’s number
= 9.6 x 104
6. 0. x 1023
= 1.60 x 10-19C
(b) An electric charge of 9.6 x 104 C liberates 1 mole of substance containing 6.0 x 1023 atoms. Determine the value of the electronic charge.
ANS: (a) If the same quantity of electricity is passed through different voltameters/electrolytes connected in series the masses of the substances liberated/deposited during electrolysis is (directly) proportional to their chemical equivalents.
(b) Let e represent the electronic charge.
e = Faraday’s constant
Avogadro’s number
= 9.6 x 104
6. 0. x 1023
= 1.60 x 10-19C
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3. State: the difference between plane polarized light and ordinary light;
two uses of polaroids
ANS: In plane polarized light, the vibrations of the particles are confined to a single plane perpendicular to the direction of propagation of light while in ordinary light, the vibrations of the particles is in all planes.
Uses of Polaroid
– sunglasses (to reduce the intensity of sunlight)
– to eliminate reflected light/glare
– sacharimetry/measurement of concentration of sugar solution.
– stress analysis/photo elasticity.
two uses of polaroids
ANS: In plane polarized light, the vibrations of the particles are confined to a single plane perpendicular to the direction of propagation of light while in ordinary light, the vibrations of the particles is in all planes.
Uses of Polaroid
– sunglasses (to reduce the intensity of sunlight)
– to eliminate reflected light/glare
– sacharimetry/measurement of concentration of sugar solution.
– stress analysis/photo elasticity.
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wing terms:
(a) tensile stress;
(b) Young’s modulus.
6. (a) Define diffusion.
(b) State two applications of electrical conduction through gases.
ANS: (a) Diffusion is the process by which substances mix with one another due to the random motion of their molecules.
(b) Applications of electrical conduction through gases include:
– In advertising industry/ Neon signs
– In lighting/ fluorescent tubes
– Identification of gases
– Cathode ray oscilloscope/ T.V. tubes.
7. (a) List two properties of cathode rays.
(b) Explain how the intensity and energy of cathode rays may be increased.
ANS: (a) Properties of cathode rays:
– They are negatively charged.
– travel in straight line in field free space.
– are deflected by electric/magnetic field.
– possess (kinetic) energy.
– possess momentum.
(b) The intensity of cathode rays may be increased by raising the temperature of the cathode /increasing the current through the heater.
They may be increased by raising the potential difference between the anode and the cathode/ the anode potential.
8. Give three observations in support of de Broglie’s assumption that moving particles behave like waves.
9. (a) Differentiate between plane polarization and interference as applied to waves.
(b) List two uses of polaroids.
ANS: (b) They are used in:
– production of 3-dimentional films
– determination of concentration of sugar solution
– polaroid cameras
– sun glasses.
10. (a) State two factors which affect the mass of elements deposited during electrolysis.
(b) List two non-electrolytes.
ANS: (a) time, current /quantity of charge, nature/ e.c.e of element.
(b) water, kerosene, petrol, benzene, ethanol.
11.
12. (a) i. State two advantages of alcohol over mercury as a thermometric liquid.
ii. When the bulb of a thermometer is placed in a beaker of hot water, the level of mercury first falls and then rises gradually. Explain this observation.
(b) List two factors, other than temperature, that affect the rate of evaporation of a liquid.
(c) A block of lead of mass 100kg in a crucible and at a temperature of 40oC was placed in an electric furnace rated 10kW. If the melting point of lead is 320oC, calculate the:
(i) quantity of heat required to heat the lead to its melting point;
(ii) additional heat energy required to melt the lead;
(iii) time taken to supply this additional energy.
(Specific heat capacity of lead = 120JKg-1 K-1
(Specific latent heat of fusion of lead = 2.5 x 104 JK-1)
(d) State two precautions necessary in an experiment to determine the specific latent heat of vaporization of water.
ANS: (a) i. Advantages of alcohol over mercury as a thermometric liquid
– lower freezing point
– cheaper
– easily expansively.
ii. the glass of the bulb of the thermometer first expands; hence the mercury level fails. The expansion of the mercury increases more than that of the glass and the liquid rises.
(b) Factors other than temperature affecting the rate of evaporation of a liquid
– wind
– humidity/ dryness of air
– nature of liquid/ viscosity /density
– area of liquid exposed
– pressure.
13. (a) State two factors which affect the angle of deviation of a ray of light through a triangular glass prism.
(b) Seven virtual images of an object are formed when two plane mirrors are inclined at an angle 0 to each other. Calculate the value of 0.
(c) By means of a ripple tank, a student was able to generate series of transverse waves by varying the frequency ofthe dipper and all the waves so generated covered a distance of 0.80 m in 0.2 s.
(i) Determine the speed, v, of the waves
(ii) Copy and complete the table given above in your answer booklet.
(iii) Plot a graph with f on the vertical axis and h -1 on the horizontal axis.
(iv) What does the slope of the graph represent?
14. The Fig. 5.1 below shows a ray of light entering and passing along an optical fibre.
(a) Calculate the refractive index of the glass in the optical fibre.
(b) Explain why the ray of light is totally internally reflected at A.
(c)
(a) tensile stress;
(b) Young’s modulus.
6. (a) Define diffusion.
(b) State two applications of electrical conduction through gases.
ANS: (a) Diffusion is the process by which substances mix with one another due to the random motion of their molecules.
(b) Applications of electrical conduction through gases include:
– In advertising industry/ Neon signs
– In lighting/ fluorescent tubes
– Identification of gases
– Cathode ray oscilloscope/ T.V. tubes.
7. (a) List two properties of cathode rays.
(b) Explain how the intensity and energy of cathode rays may be increased.
ANS: (a) Properties of cathode rays:
– They are negatively charged.
– travel in straight line in field free space.
– are deflected by electric/magnetic field.
– possess (kinetic) energy.
– possess momentum.
(b) The intensity of cathode rays may be increased by raising the temperature of the cathode /increasing the current through the heater.
They may be increased by raising the potential difference between the anode and the cathode/ the anode potential.
8. Give three observations in support of de Broglie’s assumption that moving particles behave like waves.
9. (a) Differentiate between plane polarization and interference as applied to waves.
(b) List two uses of polaroids.
ANS: (b) They are used in:
– production of 3-dimentional films
– determination of concentration of sugar solution
– polaroid cameras
– sun glasses.
10. (a) State two factors which affect the mass of elements deposited during electrolysis.
(b) List two non-electrolytes.
ANS: (a) time, current /quantity of charge, nature/ e.c.e of element.
(b) water, kerosene, petrol, benzene, ethanol.
11.
12. (a) i. State two advantages of alcohol over mercury as a thermometric liquid.
ii. When the bulb of a thermometer is placed in a beaker of hot water, the level of mercury first falls and then rises gradually. Explain this observation.
(b) List two factors, other than temperature, that affect the rate of evaporation of a liquid.
(c) A block of lead of mass 100kg in a crucible and at a temperature of 40oC was placed in an electric furnace rated 10kW. If the melting point of lead is 320oC, calculate the:
(i) quantity of heat required to heat the lead to its melting point;
(ii) additional heat energy required to melt the lead;
(iii) time taken to supply this additional energy.
(Specific heat capacity of lead = 120JKg-1 K-1
(Specific latent heat of fusion of lead = 2.5 x 104 JK-1)
(d) State two precautions necessary in an experiment to determine the specific latent heat of vaporization of water.
ANS: (a) i. Advantages of alcohol over mercury as a thermometric liquid
– lower freezing point
– cheaper
– easily expansively.
ii. the glass of the bulb of the thermometer first expands; hence the mercury level fails. The expansion of the mercury increases more than that of the glass and the liquid rises.
(b) Factors other than temperature affecting the rate of evaporation of a liquid
– wind
– humidity/ dryness of air
– nature of liquid/ viscosity /density
– area of liquid exposed
– pressure.
13. (a) State two factors which affect the angle of deviation of a ray of light through a triangular glass prism.
(b) Seven virtual images of an object are formed when two plane mirrors are inclined at an angle 0 to each other. Calculate the value of 0.
(c) By means of a ripple tank, a student was able to generate series of transverse waves by varying the frequency ofthe dipper and all the waves so generated covered a distance of 0.80 m in 0.2 s.
(i) Determine the speed, v, of the waves
(ii) Copy and complete the table given above in your answer booklet.
(iii) Plot a graph with f on the vertical axis and h -1 on the horizontal axis.
(iv) What does the slope of the graph represent?
14. The Fig. 5.1 below shows a ray of light entering and passing along an optical fibre.
(a) Calculate the refractive index of the glass in the optical fibre.
(b) Explain why the ray of light is totally internally reflected at A.
(c)
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The Fig. 5.1 below shows a ray of light entering and passing along an optical fibre.
(a) Calculate the refractive index of the glass in the optical fibre.
(b) Explain why the ray of light is totally internally reflected at A.
(c) Both optical fibre and copper wire are used to transmit data. Optical fibre is cheaper and can carry more data per second than copper wire.
State one other advantage of using optical fibre rather than copper wire to transmit
(a) Calculate the refractive index of the glass in the optical fibre.
(b) Explain why the ray of light is totally internally reflected at A.
(c) Both optical fibre and copper wire are used to transmit data. Optical fibre is cheaper and can carry more data per second than copper wire.
State one other advantage of using optical fibre rather than copper wire to transmit
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