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# NEET Physics  Electromagnetic Waves  Practice Q & A

1. Match List–I (electromagnetic wave type) with List–II (its association/application) and select the correct option from the choices given below the lists :

List – I List – II
(a)Infrared waves(i)To treat muscular strain
(c)X–rays(iii)To detect fracture of bones
(d)ultraviolet rays(iv)Absorbed by the ozone layer of the atmosphere

 (i) (ii) (iv) (iii) (iii) (ii) (i) (iv) (i) (ii) (iii) (iv) (iv) (iii) (ii) (i)

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2. A radar has a power of 1 kW and is operating at a frequency of 10 GHz. It is located on a mountain top of height 500 m. The maximum distance up to which it can detect object located on the surface of the earth(Radius of earth = 6.4 × 106 m) is :

 80 km 16 km 40 km 64 km

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3. The electric and magnetic field of an electromagnetic wave are

 in opposite phase and perpendicular to each other in opposite phase and parallel to each other in phase and perpendicular to each other in phase and parallel to each other.

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4. Out of the following options which one can be used to produce a propagating electromagnetic wave?

 A chargeless particle An accelerating charge A charge moving at constant velocity A stationary charge

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5. A red LED emits light at 0.1 watt uniformly around it. The amplitude of the electric field of the light at a distance of 1 m from the diode is

 1.73 V/m 2.45 V/m 5.48 V/m 7.75 V/m

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6. Assertion : Television signals are received through sky–wave propagation.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

 both assertion and reason are true and reason is the correct explanation of assertion. both assertion and reason are true but reason is not the correct explanation of assertion. assertion is true but reason is false. assertion and reason are false.

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7. Which of the following spectral series of hydrogen atom is lying in visible range of electromagnetic wave?

 Paschen series Pfund series Lyman series Balmer series

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8. Pick out the longest wavelength from the following types of radiations.

 Blue light Gamma rays X–rays Red light

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9. In electromagnetic spectrum, the frequencies of γ–rays, X–rays and ultraviolet rays are denoted by n1, n2 and n3 respectively then

 n1 > n2 > n3 n1 < n2 < n3 n1 > n2 < n3 n1 < n2 > n3

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10. A plane electromagnetic wave of frequency 20 MHz travels through a space along x direction. If the electric field vector at a certain point in space is 6 V m–1, what is the magnetic field vector at that point?

 2 × 10–8 T 1/2 × 10–8 T 2 T 1/2 T

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