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ELECTROMAGNETIC WAVES
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ELECTROMAGNETIC WAVES
Very Short Answer Questions
Q1. What is the average wavelength of X-rays?
Answer
Ans. X-rays Average wavelength $= ( 10+0.0001)/2 = 10.0001/2 = 5.00005nm$
Q2. Give any two uses of infrared rays.
Answer
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?
Answer
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?
Answer
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?
Answer
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?
Answer
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?
Answer
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?
Answer
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?
Answer
Ans. The displacement current is equal to charging current.Hence displacement current is 0.6 A.
Q10. Which animal can detect the infrared waves.
Q1. What does an electromagnetic wave consists of ? On what factors does its velocity in vacuum depend?
Q2. What is the Greenhouse effect and its contribution towards the surface temperature of earth?
Q1. Give the brief history of discovery of knowledge of electromagnetic waves
Q2. State six characteristics of electromagnetic waves. What is Greenhouse effect?