Topic 5 - light & EM spectrum Flashcards
What is the ‘normal’ ?
-imaginary dashed line which is perpendicular to surface, and from which all angles are measured from
How do colour filters work?
- All colours are absorbed, only a certain colour is allowed to pass through - only a certain wavelength is transmitted through the filter
How do concave lenses work ?
- Caves inward
- Spreads light outwards
- Light appears to have come from the focal point– used to correct short-sightedness
How do convex lenses work ?
- Focuses light inwards
- Horizontal rays focus onto focal point
- They are used for magnifying glasses & correct long-sightedness
Properties of EM waves
- travel at same speed in vacuum
- all transverse waves
Dangers of EM spectrum
- Higher frequency EM waves the more energy, so exposure can transfer too much energy to
cells, causing them to mutate & damage them/causing cancer
Uses and Dangers of Microwaves
- Cooking, communication
Danger –can internally heat cells
Uses and Dangers of Infra red
- Cooking, thermal imaging, short range communication, optical fibres
Dangers–can burn skin
Uses and Dangers of Ultra Violet
- Security marking, fluorescent lamps, disinfecting water
Danger– Damage to surface cells and eyes, leading to skin cancer
Uses and Dangers of X-Rays
-Observing internal structure of objects, airport/medical scanners
Dangers–cause Mutation or damage to cells in the body
Uses and Dangers of Gamma rays
-Sterilising food/medical equipment, treating cancer
Danger– cause Mutation or damage to cells in the body
Uses of radio waves
-Communications, satellite transmission broadcasting, radar and other navigation systems etc.
Uses of visible light
- vision, photography, illumination etc.
What is total internal refraction?
- light passing from denser medium into less dense medium (glass to air)
- If angle of incidence is equal to critical angle, refracted ray will pass along boundary and not exit
the medium
glass to air (Physics only)
- If angle LESS than critical angle
light refracts away from normal
