P5.3 Flashcards
How do electromagnetic waves refract?
When light (part of the electromagnetic spectrum) travels INTO a DENSER medium (air to glass)
- it slows down (wavelength decreases)
- bends TOWARDS the normal
- frequency remains
The greater the difference in density, the greater the change of direction
What happens to wavelength and frequency when a wave crosses a boundary?
If the wave speeds up (travelling into less dense medium)
- wavelength increases, frequency stays the same
How are radio waves refracted and reflected?
Sending radio waves, the Earth is curved
Reflected off of a layer of the Earth called the ionosphere
What is the difference between transmit and emit?
Transmit - let through
Emit - give out
Which EM waves are transmitted and which absorbed?
Radio and micro - transmitted by walls
Visible - absorbed by walls
UV - absorbed by walls
X rays - absorbed by atmosphere, no natural source
Gamma - from Sun and space, absorbed by atmosphere, sourced from rocks
What is a convex lens?
Converging Rays converge (refract) to a principal focus.
What is the focal length?
Length from optical centre to the principal focus
How do you correct myopia and hyperopia?
Myopia (short sighted) - can’t see distant objects, need concave lens (rays bend too much)
Hyperopia (long sighted) - can’t see close objects, need convex lens (rays meet behind the eye)
What is the wavelength of the visible light spectrum?
SHORTEST: violet indigo blue green yellow orange red LONGEST:
How does the visible light spectrum change with entering a denser object?
Shorter wavelength, slow down, refract towards normal.
e.g red refracts the most
violet the least (dispersion)
How does frequency affect refraction?
Higher frequency refracted more
What is a perceived colour?
Your receptor cells see red, green and blue.
(3 of the spectral frequencies)
- Your brain puts them together to produce a perceived colour
How do light filters work?
Red filter, absorbs all the other frequencies of light except red
What is specular reflection and diffuse?
Specular - sharp image,
Diffuse - blurred image, where reflection is on a uneven surface
