Physics Past Questions and Answers

Which of the following conditions will make water boil at a temperature of 100^oC when the atmospheric pressure is 750mmHg?

A Increase the external pressure
B Reduce the external pressure
C Heat more rapidly at the same pressure
D Reduce the external pressure by a quarter

Question 17:

Which of the following statements? i. land and sea breezes are natural convection currents. ii. convection may occur in liquids or gasses but not in solids. iii. the vacuum in a thermos flask prevents heat loss due to convection only.

A I and ii only
B I and iii only
C I and iii only
D I, ii, and iii

Question 18:

A light wave of frequency 5 x 10¹⁴Hz moves through water which has a refractive index of \(\frac{4}{3}\). Calculate the wavelength in water if the velocity of light in air is 3 x 10⁸ms^-1

A 4.5 x 10^-7m
B 6.0 x 10^-7m
C 1.7 x 10⁶m
D 2.2 x 10⁶m

Question 19:

A wave disturbance travelling in air enters a medium in which its velocity is less than that in air. Which of the following statements is true about the wave medium?

A Both the frequency of the wave and the wavelength are decreased
B The frequency of the wave is decreased while the wavelength is increased
C The frequency of the wave is unaltered while the wavelength is decreased
D The frequency of the wave is decreased while the wavelength is unaltered

Question 20:

Shadows and eclipses result from the

A Refraction of light
B Rectilinear propagation of light
C Defraction of light
D Reflection of light