A piece of blue glass heated to a high temperature and a piece of red glass at room temperature, are taken inside a dimly lit room, then

• the blue piece will look blue and red will look as usual

• red looks bnghter red and blue looks ordinary blue

• blue shines like brighter red compared to the red piece

• both the pieces will look equally red

12.

The wavelength of the radiation emitted by a body depends upon

• the nature of the surface

• the area of the surface

• the temperature of the surface

• all of the above factors

An ideal monoatomic gas is taken around the cycle ABCDA as shown in the PV diagram. The work done during the cycle is given by

• $\frac{1}{2} \mathrm{PV}$

• PV

• 2 PV

• 4 PV

Infrared radiation was discovered in 1800 by

• William Wollaston

• William Herschel

• Wilhelm Roentgen

• Thomas Young

A particle on the trough of a wave at any instant will come to the mean position after a time (T = time period)

• T/2

• T/4

• T

• 2T

The disc of a siren containing 60 holes rotates at a constant speed of 360 rpm. The emitted sound is in unison with a tuning fork of frequency

• 10 Hz

• 360 Hz

• 216 Hz

• 60 Hz

The ratio of velocity of sound in hydrogen and oxygen at STP is

• 16 : 1

• 8 : 1

• 4 : 1

• 2 : 1

In an experiment with sonometer a tuning fork of frequency 256 Hz resonates with a length of 25 cm and another tuning fork resonates with a length of 16 cm. Tension of the string remaining constant the frequency of the second tuning fork is

• 163.84 Hz

• 400 Hz

• 320 Hz

• 204.8 Hz

The apparent frequency of a note is 200 Hz, when a listener is moving wIth a velocity of 40 ms^-1 towards a stationary source. When he moves away from the same source with the same speed, the apparent frequency of the same note is 160 Hz. The velocity of sound in air in m/s is

• 340

• 330

• 360

• 320

If a liquid does not wet glass, its angle of contact is

• zero

• acute

• obtuse

• right angle