Question 586:

• JAMB 1990

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 587:

• JAMB 1990

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 588:

• JAMB 1990

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 589:

• JAMB 1990

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 590:

• JAMB 1990

Shadows and eclipses result from the

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