# Physics

• Created by: Jaz Higgs
• Created on: 04-06-14 14:34

## Nature of Light Formulae

E= hf = hc/lambda

h= plack's constant (6.63x10^-34)

f- frequency (hz)

lambda- wavelength (m)

c- speed of light in a vacuum (3.00x10^8ms-1)

eV= 1/2 mv2

eV- electron volt

m- mass

v- velocity

1eV- 1.6x10^-19J

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## Nature of Light Formulae 2

f= work function/h

f- frequency

h- planck's constant (6.63x10^-34)

hf=1/2mv max2 + work function

wm-2=w/m2

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## Waves- ENERGY

A progressive wave carries energy from one place to another without transferring any material.

For example:

1) electron-magnetic waves cause things to heat up

2) gamma rays knock electrons out of their orbit, causing ionisation

3) wave power can be used to generate electricity

PARTS OF THE WAVE

displacement- how far a point on the wave has moved from its undisturbed position

amplitude- maximum displacement

wavelength- the length of one whole wave, from crest to crest or trough to trough

period- the time taken for a whole vibration

frequency- the number of vibrations per second passing a certain point

phase difference- the amount by which one wave lags behind another

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## Reflection, refraction and frequency

reflection- the wave is bounced back when it hits a boundary

refraction- the wave changes direction as it enters a different medium

frequency= 1/period

the frequency is the inverse of the period. Get the units straight: 1hz= 1s^-1

s=d/t

speed of wave =lambda (wavelength) x frequency

v= d/t -> v=lambda/ 1/f

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