Lecture 1 - Electromagnetic spectrum

Question 1

What is light

Answer 1

• Form of energy our eyes can detect

- Electromagnetic radiation/wave

Question 2

What is an electromagnetic wave

Answer 2

Electric and magnetic components which oscillate perpendicular to its direction of propagation ( direction and motion of wave )

Question 3

What are the two types of wave

Answer 3

• Transverse wave

- Longitudinal wave

Question 4

What is a transverse wave

Answer 4

Vibrations right angle to direction of wave travel

Question 5

what is a longitudinal wave

Answer 5

vibrations parallel to direction of wave travel

Question 6

example of transverse wave

Answer 6

ripples in pond - water particles move up and down

Question 7

example of longitudinal wave

Answer 7

sound - sound particles move back and forth

Question 8

what is the electromagnetic spectrum

Answer 8

continuous range of radiation wavelengths

Question 9

how do you get visible light

Answer 9

white light passes through prism - changes into spectrum of colours

Question 10

what is a wave

Answer 10

the way in which energy is transferred between stores

vibrations/oscillations about a rest position

Question 11

what is trough

Answer 11

lowest point

Question 12

what is wavelength

Answer 12

distance between 2 peaks on same wave

Question 13

what is amplitude

Answer 13

distance between centre of wave to peak

Question 14

what is speed

Answer 14

the rate of travel of a wave in a certain direction

Question 15

what is frequency

Answer 15

the number of complete waves generated per second

Question 16

what is unpolarised light

Answer 16

both electric and magnetic fields vibrate in any randomly orientated plane perpendicular to direction of propagtion
no polarisation - electric fields oscillates in many different directions

Question 17

how many directions does polarised wave oscillate

Answer 17

one

e.g. vertical only - horizontal blocked

Question 18

which types of waves can polarisation happen for

Answer 18

transverse waves

Question 19

how does polarized light work

Answer 19

molecules specially aligned that electric field only in ONE direction - 1 axis - vertical or horizontal

Question 20

what happens with 2 polarizing filters parallel to each other

Answer 20

nothing - all light goes through- due to 2nd polarising filter
both same direction

Question 21

what happens with 2 polarizing filters perpendicular to each other

Answer 21

nothing - no light gets through - due to 2nd polarising filter

Question 22

uses of polarized light

Answer 22

• polarised sunglasses = reduces glare from reflecting surface - only lets through vertically polarised light
• polarisation of radio and microwave signals
• photo elastic stress analysis