Ray Optics and Optical Instruments — Physics STD 12 Science — Question

The angular momentum of an electron in an orbit is quantized because it is a necessary condition for the compatibility with:

The resistance of a metal increases with increasing temperature because:

What is immaterial for an electric fuse wire 

(a) Specific resistance of the wire	(b) Radius of the wire
(c) Length of the wire	(d) Current flowing through the wire

If the amplification factor of a triode (m) is 22 and its plate resistance is 6600 ohm, then the mutual conductance of this valve is mho is

(a)

(b) 25

(c)

(d)

The number of neutrons in an atom of ₉₀Th²³⁰ is:

The rms speed of oxygen at room temperature is about 500m/ s. The rms speed of hydrogen at the same temperature is about:

1. 125ms^-1
2. 2000ms^-1
3. 8000ms^-1
4. 31ms^-1

Figure represents a glass plate placed vertically on a horizontal table with a beam of unpolarised light falling on its surface at the polarising angle of 57^o with the normal. The electric vector in the reflected light on screen S will vibrate with respect to the plane of incidence in a

(a) Vertical plane

(b) Horizontal plane

(c) Plane making an angle of 45o with the vertical

(d) Plane making an angle of 57o with the horizontal

A photon in motion has a mass

(a) c/hv

(b) h/v

(c) hv

(d)

Ratio of the wavelengths of first line of Lyman series and first line of Balmer series is

(a) 1: 3

(b) 27 : 5

(c) 5 : 27

(d) 4 : 9