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

12th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20

20 x 1 = 20
1. The dimension of $\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$ is

(a)

[LT-1]

(b)

[L2T-2]

(c)

[L-1T]

(d)

[L-2T2]

2. Which of the following electromagnetic radiation is used for viewing objects through fog

(a)

microwave

(b)

gamma rays

(c)

X- rays

(d)

infrared

3. If the magnetic monopole exists, then which of the Maxwell’s equation to be modified?.

(a)

$\oint { \vec { E } .d\vec { A } } =\frac { { Q }_{ enclosed } }{ { \in }_{ 0 } }$

(b)

$\oint { \vec { E } .d\vec { A } }$=0

(c)

$\oint { \vec { E } .d\vec { A } } ={ \mu }_{ 0 }{ I }_{ enclosed }+{ \mu }_{ 0 }{ \in }_{ 0 }\frac { d }{ dt } \oint { \vec { E } .d\vec { A } }$

(d)

$\oint { \vec { E } .d\vec { l } } =-\frac { d }{ dt } { \Phi }_{ B }$

4. Which of the following is an electromagnetic wave?

(a)

α - rays

(b)

β - rays

(c)

$\gamma$ - rays

(d)

all of them

5. Let E = Eo sin[106 x -ωt] be the electric field of plane electromagnetic wave, the value of ω is

(a)

(b)

(c)

(d)

6. The electric and magnetic fields of an electromagnetic wave are

(a)

in phase and perpendicular to each other

(b)

out of phase and not perpendicular to each other

(c)

in phase and not perpendicular to each other

(d)

out of phase and perpendicular to each other

7. Who produced the electromagnetic waves first?

(a)

J.C.Bose

(b)

Marconi

(c)

Maxwell

(d)

Hertz

8. Electromagnetic waves are produced by

(a)

static charge

(b)

moving charge

(c)

an accelerating charge

(d)

chargeless particles

9. Which of the following E.M waves has the longest wavelength?

(a)

(b)

IR

(c)

X-rays

(d)

visible

10. The EM waves do not transport

(a)

energy

(b)

charge

(c)

momentum

(d)

information

11. If the velocity of light in a medium is 2.25 x 108 ms-1 then the refractive index of the medium will be

(a)

1.5

(b)

0.5

(c)

1.33

(d)

1.73

12. Dimensions of $\frac { 1 }{ { \mu }_{ 0 }{ \varepsilon }_{ 0 } }$ is

(a)

$\frac { { L }^{ 2 } }{ { T }^{ 2 } }$

(b)

$\frac { { T }^{ 2 } }{ { L }^{ 2 } }$

(c)

$\frac { T }{ L }$

(d)

$\frac { L }{ T }$

13. The wavelength of electromagnetic wave produced by Hertz experiment was

(a)

6mm

(b)

60m

(c)

6000 mm

(d)

60 cm

14. If Vg, Vx' Vm are speeds of gamma rays, X rays and microwaves respectively in vacuum, then

(a)

Vg<Vx<Vm

(b)

Vg>Vk>Vm

(c)

Vg > Vx < Vm

(d)

Vg=Vx=Vm

15. Television waves range from

(a)

54 MHz to 89 MHz

(b)

54 MHz to 890 MHz

(c)

54 MHz to 89 MHz

(d)

54 MHz to 80 MHz

16. Which of the following can be used to take photograph over long distance of

(a)

White light

(b)

(c)

(d)

Microwaves

17. Which one of the following groups of electromagnetic waves is in order of increasing frequency?

(a)

Microwaves U-V rays, X-rays

(b)

Radio waves, visible light and 1-R rays

(c)

gamma rays U-V rays radio waves

(d)

gamma rays, U-V rays radio waves

18. The spectra used for making dyes is

(a)

line spectra

(b)

continuous absorption spectra

(c)

fraunhofer spectra

(d)

band absorption spectra

19. The central core of the sun is called

(a)

chromosphere

(b)

stratosphere

(c)

photosphere

(d)

thermo sphere

20. The sun's outer layer is called _______.

(a)

chromosphere

(b)

exosphere

(c)

Photosphere

(d)

stratosphere