Light and Electromagnetic Spectrum Flashcards
What is total internal reflection?
When light is completely reflected back at a boundary between two mediums and it occurs when light meets a less dense medium at an angle of incidence larger than the critical angle
What is the critical angle?
The angle of incidence which causes the angle of reflection to be 90 degrees
What determines the colour of visible light waves?
The wavelength and frequency of the light waves
What colour of visible light had the highest frequency?
Blue
What colour of visible light has the largest wavelength?
Red
What is specular reflection?
Rays are reflected from a smooth surface in a single direction
What is diffuse reflection?
Reflection from a rough surface which causes scattering
How does a red colour filter work?
A red filter absorbs all wavelengths of light other than those in red range of the spectrum and this means only red light passes through the filter
What is opaque?
Not see through
What governs the colour of an opaque object?
Different objects reflect different wavelengths of light by different amounts and the wavelength that are most strongly reflected determine the colour
What happens to the wavelengths of light that aren’t reflected by an opaque object?
Any wavelengths that aren’t reflected are absorbed by the object
What colour does an object appear if all wavelengths are reflected by equal amounts?
White
What colour does an object appear if all wavelengths are absorbed?
Black
What do all bodies emit and absorb?
Infrared radiation
What happens to the quantity of infrared radiation emitted by an object as temperature increases?
The hotter the object, the more infrared radiation it will emit
What happens to the type of radiation emitted by an object as temperature increases?
The hotter the body the shorter the wavelength of radiation released?
What is required for a body to be at a constant temperature?
The body would need to emit radiation at the same rate it absorbs it - it needs to radiate at the same average power that it absorbs
What distributes any emissions that depends on temperature?
Intensity and wavelength
What is meant by intensity?
The power transferred per unit area, a measure of the energy transferred by a wave
What will happen if the average power that a object radiates is less than absorbs?
The temperature of the object will decrease
What can be said about the rates of emission and absorption for a body increasing temperature?
The body is absorbing radiation faster than it’s emitting it
What factors that affect the temperature of the Earth?
The Earths rate of absorption and emission of radiation and the amount of reflection of radiation into space
How does the Earths atmosphere affect radiation?
The atmosphere largely absorbs or reflects radiation from the sun, preventing it from reaching Earth and some radiation, however is allowed to pass through and warms the earth
What happens to the radiation emitted from the Earth?
It’s absorbed and re-emitted in all directions by greenhouse gases, resulting in the greenhouse effect which warms the earth
