When the two waves y1 = a sin ωt and y2 = a cos ωt are superimposed, then resultant amplitude is
a
2a
A train moves towards a stationary observer with speed 34 ms-1 . The train sounds a whistle and its frequency registered by the observer is v1 , If the train's speed is reduced to 17 ms-1, the frequency registered is v2. If the speed of sound is 340 ms-1 , then the ratio v1 /v2 is
2
Two vibrating strings of the same material but lengths L and 2 L have radii 2r and r respectively. They are stretched under the same tension. Both the strings vibrate in their fundamental modes, the one of length L with frequency v1 and the other with frequency v2 . The ratio v1 / v2 is
2
4
8
1
The temperature, at which centigrade and Fahrenheit scales give the same reading, is
- 40°
40°
- 30°
30°
A brass rod of length 500 mm and diameter 3 mm is joined to a steel rod of same length and diameter at 50°C. If the coefficients of linear expansion of brass and steel are 2.5 x 10-5 ° C-1 and 1.25 x 10-5 ° C-1 , then change in length of the combined rod at 200°C is
2.4 mm
2.8 mm
3.2 mm
3.6 mm
A copper block of mass 4 kg is heated in a furnance to a temperature 425°C and then placed on a large ice block. The mass of ice that will melt in this process will be (Specific heat of copper = 500 J kg-1 ° C-1 and heat of fusion of ice = 336 kJ kg-1 )
0.5 kg
1 kg
1.5 kg
2.5 kg
A block of ice at - 10°C is slowly heated and converted to steam at 100°C. Which of the following curves represents this phenomenon qualitatively ?
The pressure and density of a diatomic gas change adiabatically from (P1 , ρ1) to (P2 , ρ2) . If , then should be
16
32
64
128
One mole of an ideal gas at an initial temperature of T K does 6R joules of work adiabatically. If the ratio of specific heats of this gas at constant pressure and at constant volume is 5/3, then final temperature of the gas will be
(T − 4) K
(T + 4) K
(T − 2.4)K
(T + 2.4) K
In which mode of transmission, the heat waves travel along straight line with the speed of light?
thermal radiation
forced convection
natural convection
thermal conduction
A.
thermal radiation
The energy emitted by a body, in the form of radiation on account of its temperature, is called thermal radiation. These radiations are heat radiations and travel along straight lines with the speed of light.