1. When ultraviolet light falls on a _______ surface, electrons are emitted.
(A) ceramic
(B) non-metal
(C) wooden
(D) metal
2. Emission of electrons due to effect of light is called as _______ emission.
(A) thermionic
(B) secondary
(C) electric
(D) photoelectric
3. Photoconductive materials offer _____ resistance in the absence of light.
(A) low
(B) high
(C) very low
(D) none of these
4. In photo-sensitive material the amount of produced voltage depends on _______.
(A) intensity of light
(B) size of semiconductor
(C) nature of semiconductor
(D) All of these
5. Thermocouple is used for measuring _______.
(A) temperature
(B) resistance
(C) velocity
(D) flow
6. Thomas A. Edison invented incandescent lamp in _______.
(A) 1879
(B) 1897
(C) 1987
(D) 1978
7. _______ filament is used in incandescent lamp.
(A) carbon
(B) copper
(C) tungsten
(D) silver
8. Fluorescent tube operates on _______ working temperature.
(A) 300℃
(B) 400℃
(C) 500℃
(D) 600℃