Chapter 11 - Waves 1 (pt2)

Question 1

EM waves

Answer 1

Transverse waves made up of electric and magnetic fields oscillating at right-angles to each other

Question 2

Wavelengths of visible light

Answer 2

400-700nm

Question 3

EM Spectrum

Answer 3

Radio waves   - longest wavelength
Microwaves
Infrared
Visible
Ultraviolet
X-rays
Gamma rays   - highest frequency

Question 4

Uses of microwaves, infrared and gamma rays

Answer 4

Micro: Mobile phones
Infrared: TV remotes
Gamma: Medical treatments

Question 5

Two main properties of EM waves

Answer 5

They are transverse so can be reflected, refracted, polarised and diffracted
They travel at the speed of light

Question 6

Refractive Index

Answer 6

n = c/v
Refractive index of a material = speed of light in a vacuum/speed of light in the material
Unitless quantity

Question 7

Snell’s Law

Answer 7

n1 sinθ1 = n2 sinθ2

where θ is the acute angle to the normal and n is the refractive index

Question 8

Refractive Index of air

Answer 8

1

Question 9

Total Internal Reflection

Answer 9

Where light is travelling from a medium with a higher refractive index to a lower at an incident angle greater than the critical angle
All of the light is reflected back into the medium
At the critical angle, the light continues along the boundary

Question 10

Critical angle equation

Answer 10

Sin C = n2/n1

Question 11

Polarising Filters

Answer 11

One polarises a wave in the polarising plane

Two with polarising planes in the same direction allow all light through, two at 90 allow no light through