Light Flashcards
Draw a reflection diagram
Draw a periscope diagram
Reflection is ..
- upright
- a virtual image
- laterally inverted
- the same size
- equal distance (equal distance inversion) behind the mirror as the object is in front
I =
R =
Angle of incidence
Angle if reflection
Always draw the … 90 degrees to the mirror
Normal (dotted line)
Angle of incidence =
Angle of reflection
Waves …
Transfer energy but not matter
Peak of a wave
Point on a wave with the highest displacement. Adjacent peaks are separated by one wavelength.
Trough of wave
Point on a wave with the lowest displacement. Adjacent troughs are separated by one wavelength.
Amplitude of wave
Maximum displacement above or below the undisturbed position
Wavelength
The distance from peak to adjacent peak or trough to adjacent trough
Transverse wave
Vibrations are perpendicular to the direction of energy transfer
Longitudinal wave
Vibrations are parallel to the direction of energy transfer
Frequency
The number of vibrations per second. Measured in Hertz (Hz)
Time period (t)
The time for 1 wave to be produced. Measured in second (s)
Frequency = 1/time period
Diffraction
The spreading out of a wave
Waves with longer wavelengths diffract more
The amount of diffraction that occurs when a wave moves through a gap depends on the relative sizes of the gap and the wavelength
If the gap and wavelength are about the same size, there is a large amount of diffraction
Refraction
The bending of light when travelling from one medium into another. Refraction occurs because light changes speed when it changes medium.
When light slows down after hitting a medium
It bends (refracts) towards the normal and vice versa
Snell’s law equation
Sin i / Sin r = n (refractive index)
n = speed of light / speed of light in glass
n = 3.00 x 10 (pw8) / 2.00 x 10 (pw8)
n = 1.5
Refractive index of water
1.33
Speed of light in air
3.0 x 10(8)m/s
How yo calculate the refractive index of the glass prism
Measure the angle of incidence when the angle of refraction is 90 degrees, the i is the critical angle
Then use SinC = 1/n to calculate the refractive index
When travelling from glass to air the light … And bends away from the normal
Speeds up
Fibre optic cables
This is a cable made up of super-thin filaments of glass or other transparent materials that can carry beams of light therefore data can be transmitted at the speed of light
Advantages of fibre optic cables over copper cables
Carry more information
No electro-magnetic interference
Unable to hack conversations
describe what happens when a light is shone at a certain angle in a prism
- the em spectrum is formed in and through the other side of the prism
- blue comes at the bottom as it has a smaller wavelength
- red comes at the top as it has a greater wavelength
- EM spectrum forms in the middle of the blue and red
- both colours speed up when they leave the prism to the same speed
- blue has a greater refractive index and slows down more and refracts more in the prism
- red has a smaller refractive index than blue light and is faster in the prism than blue light therefore refracts less
describes what happens in a periscope prism
total internal reflection is happening. no mirrors are used. the angle of the prisms have to be larger than the critical angle of 42 degrees otherwise a distorted image would be seen at the receiving end of the periscope
why aren’t mirrors used in a pericope prism
as metal and glass will age over time and decrease in quality. this method can never age.
