# ELECTROMAGNETIC WAVES (3 Marks)

Urban and Civil

Nov 16, 2013 (4 years and 7 months ago)

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ELECTROMAGNETIC WAVES (3 Marks)

1 Mark Questions:

Q1.

A plane electromagnetic wave travel in vacuum along z
-

direction. What can

You

say
about the direction of electric
& magnetic field vectors?

Q2. Write the use of
infrared waves
? What
is the
range of there

Wavelength ?

Q3
. Arrange the following in descending order of the wavelength.

X
-
rays, radio wave, visible spectrum
, infrared light.

Q4
.
Which part of electromagnetic spectrum has largest penetrating power?

Q5
. Which part of electroma
gnetic spectrum is absorbed from sunlight by ozone

layer?

Q6
.

Name the electromagnetic radiation used to destroy cancer cells and write its

Frequency

range?

Q7
. Name the part of electromagnetic spectrum of wavelength 10
-
2

m and

mention its applications?

Q8. Welders wear special goggles or face masks with glass windows to protect
their eyes from electromagnetic radiation. Name the radiations and write the
range of their frequency.

2 Marks Questions
:

Q1. How are X
-
rays pro
duced? Write their two important uses.

Q2. How are microwaves produced? Write their two important uses.

Q3. Name the electromagnetic radiations having the wavelength
range

from 1nm

to 700nm.Give its two important properties?

3 Marks Question

Q
1.

(
i)

Describe briefly how electromagnetic wa
ves are produced by oscillating

charge?

(ii) Give one use of each of the following

(a)

Microwaves

(b)

Ultraviolet rays

(c)

Infrared rays

(d)

Gamma rays

Answer keys

1 Mark Question

A1. Direction of
electric and magnetic field vectors are along X and Y direction
respectively.

A2. Hot objects and molecules are the sources

of infrared wave
s
. Range of
wavelength = 7 x 10
-
7

m to 10
-
3

m.

A3. Radio wave >Infrared > Blue light > Xray.

A4.
X rays

A5. Ultravio
let rays.

A6. Xrays.

Frequency range = 10
18

Hz to 10
20

Hz

A7. Microwaves. They are used in RADAR communication.

A8. Ultraviolet rays.

The range of U.V. rays is 4 x 10
-
7

m (400nm) to 6 x 10
-
10
m (0.6nm)

Answer keys : 2 marks question:

A1. X
-
rays can be
produced by colliding fast moving electron beam on metal

Target.

USES: (i)medical diagnosis (ii) study of crystal structure.

A2. Microwaves are produced by oscillating current in the vacuum tubes like

klystrons

& magnetrons.

USES:

(i) In radar communication.

(ii) In analysis of molecular and atomic structure.

A3. Infrared waves have the wavelength between 1nm to 700nm.

APPLICATIONS:
(i)
In remote control of TV, VCR

etc.

(
ii) In photography in thin mist.

3 marks questions:

A1. The
oscillating charge accelerates and hence equivalent to varying electric
current which in turn changes the magnetic field. This leads to production of
electric field. Thus oscillating charge pr
oduces time varying electric and magnetic
fields. Hence , electromagnetic waves produced.