Physics - Study Mode

[#871] For photoelectric effect to take place, the metal used as the cathode should have ________
Correct Answer

(C) Low work function

Explanation

Solution: The photoelectric effect is the propensity of high energy electromagnetic radiation to eject electrons from a given material. The photoelectric effect has been utilized in devices called photocells, consisting of two electrodes in a sealed vacuum tube. By coating one electrode (the photocathode) with a alkali metal of low work function, a photo current could be generated even from visible light. Work function is the minimum energy needed to remove an electron from the surface of a material.

[#872] Which phenomena shows the particle nature of light?
Correct Answer

(C) Photoelectric effect

Explanation

Solution: Most commonly observed phenomena with light can be explained by waves. But the photoelectric effect suggested a particle nature for light.

[#873] According to the quantum theory of light, the energy of light is carried in discrete units are called
Correct Answer

(D) Photons

Explanation

Solution: According to the quantum theory of light, energy of light is carried in discrete units called photons.

[#874] Photon is the fundamental unit/quantum of
Correct Answer

(D) Light

Explanation

Solution: A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation. The modern photon concept was developed gradually by Albert Einstein.

[#875] During hot weather, the fan produces a feeling of comfort. This is because
Correct Answer

(C) Our perspiration eva-porates rapidly

Explanation

Solution: During hot weather, the fan produces a feeling of comfort. This is because our perspiration evaporates rapidly.