Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

Sodium and copper have work functions 2.3 eV and 4.5 eV respectively. Then the ratio of the wavelengths is nearest to?

X-ray from a Coolidge tube is incident on a thin aluminium foil. The intensity of the X-ray transmitted by the foil is found to be I₀. The heating current is increased to increase the temperature of the filament. The intensity of the X-ray transmitted by the foil will be:

1. zero
2. < I₀
3. I₀
4. > I₀

An electric field is applied to a semiconductor. Let the number of charge carriers be n and the average drift speed be v. If the temperature is increased,

According to Bohr's Model, which is not possible energy value of emitted photon by hydrogen atom :

Lorentz force is:

A coil of N turns and mean cross-sectional area A is rotating with uniform angular velocity w about an axis at right angle to uniform magnetic field B. The induced e.m.f. E in the coil will be

(a) NBA sinwt

(b) NB w sinwt

(c) NB/A sinwt

(d) NBA w sinwt

The e.m.f. of a cell is E volts and internal resistance is r ohm. The resistance in external circuit is also r ohm. The p.d. across the cell will be

(a) E/2

(b) 2E

(c) 4E

(d) E/4

To maintain a steady current through the conductor, some external device must do work. What does the external device provide?

It becomes possible to define potential at a point in an electric field because electric field: