Electric Charges and Fields — Physics STD 12 Science — Question

In a metal, the separation between conduction band and valence band is of the order:

In a semiconductor, the forbidden energy gap between the valence band and the conduction band is of the order is:

The dimensions of surface charge density is:

Which of the following is the correct statement regarding electrochemical cell?

The eye can detect 5 × 10⁴ photons per square metre per sec of green light (l = 5000 Å) while the ear can detect  . The factor by which the eye is more sensitive as a power detector than the ear is close to

(a) 5

(b) 10

(c) 106

(d) 15

The resistance of a wire of iron is 10 ohms and temp. coefficient of resistivity is  5 . At  20 it carries 30 milliamperes of current. Keeping constant potential difference between its ends, the temperature of the wire is raised to 120. The current in milliamperes that flows in the wire is

(a) 20

(b) 15

(c) 10

(d) 40

When a white light passes through a hollow prism, then

(a) There is no dispersion and no deviation	(b) Dispersion but no deviation
(c) Deviation but no dispersion	(d) There is dispersion and deviation both

Total internal reflection of a ray of light is possible when the ( = critical angle, i  =  angle of incidence)

(a) Ray goes from denser medium to rarer medium and

(b) Ray goes from denser medium to rarer medium and

(c) Ray goes from rarer medium to denser medium and

(d) Ray goes from rarer medium to denser medium and

With increase in temperature the conductivity of: