4.4.2: Electromagnetic Waves

Question 1

Electromagnetic waves

Answer 1

Transverse progressive waves consisting of magnetic and electric fields which oscillate at 90° to each other.

Question 2

Order of electromagnetic spectrum

Answer 2

Radio (10^3 m)
Microwave (10^-2 m)
Infrared (10^-5 m)
Visible (400-750 nm)
Ultraviolet (10^-8 m)
X-ray (10^-10 m)
Gamma ray (10^-12 m)

Question 3

Refractive Index

Answer 3

n = c/v
refractive index = speed of light / speed of light in medium

Question 4

Interface between media

Answer 4

For a ray of light leaving medium with refractive index n1, at an angle of θ1, into a new medium with refractive index n2, the angle θ2 can be calculated. All θ are measured relative to the normal.
n1sinθ1=n2sinθ2

Question 5

Total Internal Reflection

Answer 5

TIR occurs at a boundary between two transparent media, with no refraction- all of the light is reflected. The light must be travelling from a material with a higher refractive index/ optical density to a material with lower refractive index/ optical density. The angle of incidence must be above the critical angle C.
sinC = 1/n
where C is the critical angle and n is the refractive index the ray is travelling into.