The frequencies of X-rays, -rays and ultraviolet rays are respectively a, b and c. Then :
(1) a < b, b < c
(2) a > b, b > c
(3) a > b, b > a
(4) a < b, b > c
A plane electromagnetic wave of frequency 40 MHz travels in free space in the x-direction. At some point and at some instant, the electric field has its maximum value of 750 N/C in y-direction. The wavelength of the wave is
(1) 3.5 m
(2) 5.5 m
(3) 7.5 m
(4) 9.5 m
The waves used in telecommunication are
(1) infrared
(2) visible light
(3) microwaves
(4) ultraviolet rays
I: | Light can travel in vacuum but sound cannot do so. |
II: | Light is an electromagnetic wave and sound is a mechanical wave. |
1. | Both I and II are true and II is the correct explanation of I. |
2. | Both I and II are true but II is not the correct explanation of I. |
3. | I is true but II is false. |
4. | I is false but II is true. |
The wave impedance of free space is
(1) 0
(2) 376.6
(3) 1883
(4) 3776
The frequency 1057 MHz of radiation arising from two close energy levels in hydrogen belongs to
(1) radio waves
(2) infrared waves
(3) micro waves
(4) -rays
The wave associated with 2.7 K(kelvin) belongs to
(1) radio waves
(2) micro waves
(3) ultraviolet ways
(4) infrared waves
The penetration power of X-ray increases with the increases in its :
(1) velocity
(2) intensity
(3) frequency
(4) wavelength
The shortest wavelength of X-rays emitted from an X-ray tube depends upon
(1) nature of the gas in the tube
(2) the voltage applied to the tube
(3) current in the tube
(4) nature of the target of the tube
X-rays are not used for radar purposes, because they are not
(1) reflected by target
(2) partly absorbed by the target
(3) electromagnetic waves
(4) completely absorbed by the target