ELECTROMAGNETIC WAVES

Very Short Question Answers

Q1. What is the average wavelength of X-rays?

Ans.

X-rays  Average wavelength $=  ( 10+0.0001)/2   =   10.0001/2   = 5.00005nm$


Q2. Give any two uses of infrared rays.

Ans.

Uses of infrared rays:1) used in remote switches   2) military purposes   .3) infrared detectors 


Q3. If the wavelength of electromagnetic radiation is doubled, what happens to the energy of photon?

Ans.

Energy of photon   $E \,=\,hc/λ $
$\therefore E_{1}/E_{2}   =  (λ_{2}/λ_{1})$

$E_{2}/E = λ/2λ$

$E_{2}=E/2$
Energy is halved.


Q4. What is the principle of production of electromagnetic waves?

Ans.

Principle:Accelerated charges radiate energy in the form of electromagnetic waves.

So accelerated charge is the source of electromagnetic wave.


Q5. What is the ratio of speed of infrared rays and ultraviolet rays in vacuum?

Ans.

Both infrared and UV rays travel with a velocity $3 \times10^{8} $$ m/s$ in vacuum.
 Hence ratio of their speeds is $1: 1$


Q6. What is the relation between amplitudes of the electric and magnetic fields in free space for an electromagnetic wave?

Ans.

The ratio of amplitudes of electric to magnetic fields in free space is   $\frac{E_{0}}{B_{0}}   = C$
  C = velocity of light in free space.


Q7. What are the applications of micro waves?

Ans.

 Micro waves are used in 1) in microwave ovens  2) in radar systems used in aircraft navigation     
3) measuring the speed of vehicles.


Q8. Micro waves are used in radars. Why?

Ans.

Due to their short-wave lengths, they are suitable for the radar systems used in air – craft   navigation.


Q9. The charging current for a capacitor is 0.6 A. What is the displacement current across its plates?

Ans.

The displacement current is equal to charging current.Hence displacement current is 0.6 A.


Q10. Which animal can detect the infrared waves.

Ans.

Snakes