UPSC 2002 › Science & Technology › Physics

A solid cube just gets completely immersed in water when a 0.2 kg mass is placed on it. If the mass is removed, the cube is 2 cm above the water level. What is the length of each side of the cube?

Consider the following natural phenomena:

1. Terrestrial heating
2. Reflection of light
3. Refraction of light
4. Diffraction of light Due to which of these phenomena is mirage formed?

Consider the following statements:

1. Light of longer wavelength is scattered much more than light of shorter wavelength.
2. The speed of visible light in water is 0.95 times its speed in vacuum.
3. Radio waves are produced by rapidly oscillating electrical currents.
4. To detect over-speeding vehicles, police use the Doppler effect of reflected short radio waves.

Which of these statements are correct?

A hollow sphere of radius R, a hollow cube of side R and a thin circular plate of radius R, made up of the same material, are all heated to 20 °C above room temperature. When left to cool in the room, which of them will reach the room temperature first?

Assertion (A): An iron ball floats on mercury but gets immersed in water.

Reason (R): The specific gravity of iron is more than that of mercury.