#### 12th Standard Physics Electromagnetic Waves English Medium Free Online Test One Mark questions with Answer Key 2020 - 2021

12th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20
20 x 1 = 20
1. If the amplitude of the magnetic fi eld is 3 × 10−6 T, then amplitude of the electric fi eld for a electromagnetic waves is

(a)

100 Vm−1

(b)

300 V m-1

(c)

600 V m-1

(d)

900 V m-1

2. Th e electric and the magnetic field, associated with an electromagnetic wave, propagating along X axis can be represented by

(a)

$\vec { E } ={ E }_{ 0 }\hat { j }$ and $\vec { B } ={ B }_{ 0 }\hat { k }$

(b)

$\vec { E } ={ E }_{ 0 }\hat { k }$ and $\vec { B } ={ B }_{ 0 }\hat { j }$

(c)

$\vec { E } ={ E }_{ 0 }\hat { i }$ and $\vec { B } ={ B }_{ 0 }\hat { j }$

(d)

$\vec { E } ={ E }_{ 0 }\hat { j }$ and $\vec { B } ={ B }_{ 0 }\hat { i }$

3. A radiation of energy E falls normally on a perfectly refl ecting surface. Th e momentum transferred to the surface

(a)

$\frac{E}{c}$

(b)

2$\frac{E}{c}$

(c)

Ec

(d)

$\frac { E }{ { c }^{ 2 } }$

4. Which one of them is used to produce a propagating electromagnetic wave?.

(a)

an accelerating charge

(b)

a charge moving at constant velocity

(c)

a stationary charge

(d)

an uncharged particle

5. Which of the following is NOT true for electromagnetic waves?

(a)

it transport energy

(b)

it transport momentum

(c)

it transport angular momentum

(d)

in vacuum, it travels with different speeds which depend on their frequency

6. Which of the following electromagnetic waves has the highest frequency?

(a)

(b)

micro waves

(c)

X- rays

(d)

૪-rays

7. Which EM waves are used in medicine to destroy cancer cells?

(a)

(b)

IR

(c)

૪ rays

(d)

UV rays

8. The existence of E.M. waves was confirmed experimentally by

(a)

Hertz

(b)

Maxwell

(c)

Huygens

(d)

Planck

9. A magnetic field is produced by

(a)

a changing electric field

(b)

a moving charge

(c)

both of them

(d)

none of them

10. Electromagnetic waves are discovered by

(a)

Hertz

(b)

Maxwell

(c)

Lenz

(d)

Huygens

11. The phase difference between electric and magnetic field vectors in the electromagnetic waves?

(a)

$\frac{\pi}{4}$

(b)

$\frac{\pi}{2}$

(c)

$\pi$

(d)

zero

12. The unit of μoεo is

(a)

m S-1

(b)

m2 S-2

(c)

m-1 s

(d)

m-2 S-2

13. The velocity of light is maximum in

(a)

Diamond

(b)

Water

(c)

Vacuum

(d)

Glass

14. Which one of the following is not an electromagnetic waves?

(a)

Gamma rays

(b)

X-rays

(c)

Beta rays

(d)

Microwaves

15. Which of the following is used to study crystal structure?

(a)

microwave

(b)

infrared rays

(c)

ultraviolet rays

(d)

X-rays

16. A pure red glass plate when placed in the path of the light absorbs everything except__________.

(a)

yellow

(b)

black

(c)

green

(d)

red

17. The waves used in physiotherapy is ___________.

(a)

I-R rays

(b)

U-V rays

(c)

μ - waves

(d)

૪-rays

18. __________discovered electromagnetic induction.

(a)

(b)

Maxwell

(c)

Ampere

(d)

Hertz

19. The relation between velocity of light, permeability and permittivity of free space in________.

(a)

${ C }^{ 2 }=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$

(b)

$C=\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$

(c)

${ \mu }_{ 0 }={ \varepsilon }_{ 0 }c$

(d)

${ \varepsilon }_{ 0 }={ \mu }_{ 0 }c$

20. ૪-rays are produced by _______.

(a)

(b)

high energy electrons

(c)

incandescent solids

(d)

electronic devices