(SP5) Light and the Electromagnetic Spectrum Flashcards
Law of reflection
A light ray will bounce of an object at the same angle that it strikes at it
The angle of incidence = The angle of reflection
Refraction is…
the change in direction, which happens at the interface between the 2 media.
Refraction diagrams in 2 different medias
From rarer to denser, towards
From denser to rarer, away
Critical angle is…
the angle of incidence where the angle of refraction equals to 90 degrees.
Total Internal Reflection (TIR)
Light passing through a semi-circular glass block will totally internally reflect after it reaches a criticle angle
White light is…
made up of many colours, which we can see if we pass white light through an optical prism. Different frequencies of visible light cause us to see different colours.
Different colours will change speed by different amounts => different angles
Diffuse reflection is…
when reflected light is scatter in all direction
by rough surfaces
Specular reflection is…
when the light is reflected evenly by very smooth objects (eg mirror)
What happens when white light hits a coloured surface?
Some of the colours that make it up are absorbed and some are reflected.
eg a yellow objects looks yellow because it reflects yellow light and absorbs all the other colours.
The power of a lens is…
how much it bends light that passes through it. A more powerful lens is more curved and bends the light more.
The focal length is…
the distance between the focal point and the centre of the lens.
Types of lenses (give the description too)
1) Converging - fatter in the middle than the edges. Makes parallel rays converge at the focal point and creats a real image
2) Diverging - thinner in the middle than the edges. Makes parallel rays spread out and creats virtual images.
Electromagnetic waves are…
transverse waves and travel at the same speed in vacuum (3 x 10^8m/s). Like all waves they transfer energy from a source to an observer.
Discovering of Infrared
British astronomet William Herschel discovered infrared radiation. He put dark, coloured filters on his telescope to help him observe the Sun rays safely. He noticed different coloured filters heated up his telescope to different extents.
Electromagnetic spectrum (list the range)
the full range of electromagnetic waves.
- Gamma rays
- X-rays
- Ultraviolet
- Visible light
- Infrared
- Microwaves
- Radio waves
