Given below are two statements: 

Assertion (A):	Light can travel in vacuum but sound cannot do so.
Reason (R):	Light is an electromagnetic wave and sound is a mechanical wave.

1.	Both (A) and (R) are True and (R) is the correct explanation of (A).
2.	Both (A) and (R) are True but (R) is not the correct explanation of (A).
3.	(A) is True but (R) is False.
4.	(A) is False but (R) is True.

The wave impedance of free space is

(1) 0 $\Omega$

(2) 376.6 $\Omega$

(3) 1883 $\Omega$

(4) 3776 $\Omega$

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) $\gamma$-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

The energy of the X-rays photon is 3.3$\times {10}^{-16}$J. Its frequency is :

(1) $2\times {10}^{19} Hz$

(2) $5\times {10}^{18} Hz$

(3) $5\times {10}^{17} Hz$

(4) $5\times {10}^{16} Hz$

A plane electromagnetic wave $E_z=100 \cos (6\times {10}^{8}t+4x) V/m$ propagates in a medium of dielectric constant

(1) 1.5

(2) 2.0

(3) 2.4

(4) 4.0