EMW

Question 1

displacement current

Answer 1

the current that comes into play in region where electric flied and electric flux is changing

Question 2

why are microwaves considered suitable for radar system

Answer 2

Microwaves have longer wavelengths and low frequencies. So they can be focussed along a straight line without much deviation and thus do not bend around corners of any obstacle coming in their path

Question 3

welders use special goggles

Answer 3

The special glass goggles absorb the ultra-violet light and thus save the eyes from the harmful effect of ultra-violet light.

Question 4

what is the source of energy of EM waves

Answer 4

energy is contributed by electric and magnetic field

Question 5

why infrared is known as heat waves

Answer 5

Infra-red waves are also known as heat waves because they raise the temperature of the object on which they fall.

Question 6

What do you understand by the statement, “Electromagnetic waves transport momentum” ?

Answer 6

This means that when an e.m. wave travels through space with energy U and speed c, then it transports linear momentum p =
U/c. If a surface absorbs the waves completely, then momentum ‘p’ is delivered to the surface. However, if the surface reflects the wave, then momentum delivered by both incident and reflected wave adds on to give a momentum of ‘2p’.

Question 7

how are electromagnetic waves produced and their source

Answer 7

Suppose an accelerated charged particle oscillates in space, definitely, it will produce a time-varying electric field and a time-varying magnetic field. This process will repeat again and again
Hence, the accelerating charged particles are the source of electromagnetic waves.

.

Question 8

how do you convince yourself that electromagnetic waves carry energy

Answer 8

The EM waves are produced by the accelerated charge. The electron jumping from its outer to inner orbits radiates EM waves. These EM waves are propagated as electric and magnetic fields oscillating in mutually perpendicular directions which is cause of momentum and energy.

Question 9

high wavelength - low wavelength
low frequency to high frequency

reading
maths
is
very
useful
example
geometry

Answer 9

radio waves
microwaves
infrared
visible rays
uv
x-ray
gamma rays

Question 10

how are the magnitudes of the electric and magnetic fields related to velocity of the em wave

Answer 10

the ratio of magnitude of electric field to the magnitude of magnetic field

Question 11

how are X- rays produced

Answer 11

bombarding of metal targets by high energy e-

Question 12

MAXWELL’S EQUATIONS

Answer 12

1. gauss’s law of electrostatics
2. gauss’s law of magnetostatics
3. faraday’s law of EMI
4. ampere’s - maxwell’s circuital law

Question 13

radiation pressure

Answer 13

since Emw have momentum an EM wave also exerts a pressure

Question 14

RADIO WAVES
production:
frequency:
wave length:
uses:

Answer 14

rapid acceleration and deceleration of electrons in aerials
500 kHz- 1000 kHz
>0.1 m
1. AM- shortwave band- 530kHz-171-kHz
2. TV- 54mHz- 890MHz
3. FM- 88MHz- 108Mhz

Question 15

MICROWAVE
production:
frequency:
wave length:
uses:

Answer 15

spcl vaccum tubes called glystron, magnetron and gunn diodes
gigahertz - 10^12 - 10^9hz
0.1m to1mm
radar system
speed guns for balls
microwave

Question 16

how microwave heat food up

Answer 16

the fre of microwa veis selected to match the resonant freq of water molecules
so energy from the waves is transferred eff to K.E of molecules
t his rasies temp of any food contaaing water

Question 17

INFRARED
production:
frequency:
wave length:
uses:

Answer 17

vibration of atoms and molecules
10^12 - 10^14hz
1mmto 700nm
1. earth satellitr
2. electronic devise (semiconducting light emmiter)
3. tv remotes
4. green house effect

Question 18

why IR is called HEAT WAVES

Answer 18

water molecules present in most material absorb IR
THEIR thermal motion increases and heat up and heat their surrounding

Question 19

VISIBLE RAYS
production:
frequency:
wave length:
uses:

Answer 19

ELECTRON in atom emit light when they move from one enrgy level to a lower enegey lecvel
4X10^14 to 7X10^14
700nm to 400nm

Question 20

UV
production:
frequency:
wave length:
uses:

Answer 20

INNER SHELL e- moving from one enrgy level to another
10^14 - 10^17
4X10^–7m - 1nm
1. LASIK
2. water purification

Question 21

X -ray
production:
frequency:
wave length:
uses:

Answer 21

bombar a metal with high energy e-
10^-8 to 10^-12 hz
1nm to 10^-3nm
1. study of crystal structure
2. treatment of cancer
3. diagnostic tool

Question 22

Gamma rays
production:
frequency:
wave length:
uses:

Answer 22

radio active decay of nucleus
10^19- 10^23
<10^-3
destroy cnacer cells

Question 23

WHICH wave is called Short wave length radio waves

Answer 23

microwaves