Nature of Light

Question 1

Spectra

Answer 1

ROYGBIV = Richard of York Gave Battle In Vain. …IV = roman 4, = 400nm, R=700nm.

Question 2

Plane Polarised light

Answer 2

Oscillations only occurring in the one plane.

Question 3

Radiation Flux (Wm-2) – also known as Intensity

Answer 3

The amount of energy landing on a unit area in unit time (Flux = Power / Area).

Question 4

Luminosity (W)

Answer 4

Rate of which energy of all types is radiated by an object in all directions.

Question 5

Electronvolt (eV)

Answer 5

The energy change of an electron when it moves through a potential difference of 1 volt.

Note: It’s called electron-volt but it’s a unit of Energy.

1 volt = 1J/C and the charge on an electron is 1.6 x 10-19 C
then 1eV = 1.6 x 10-19 J.

Question 6

Work function (ϕ, J)

Answer 6

The minimum energy required to release an electron from the surface of a metal by the photoelectric effect.
Energy = hf – φ
Energy = ½ mv2

Question 7

Threshold frequency (Hz)

Answer 7

The lowest frequency of radiation that will result in the emission of electrons from a particular metal surface.

Usually this is in the ultraviolet region of the electromagnetic spectrum.

Question 8

Photon

Answer 8

A particle representing a quantum or packet of electromagnetic radiation (e.g. light). A photon carries energy proportional to the radiation frequency (E = hf) but has zero rest mass.

Question 9

Energy Level

Answer 9

Is a discrete, allowed energy level that an atom/electron can reside at.