P14

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What happens when plane waves reflect from a flat barrier?
The reflected waves are at the same angle to the barrier as the incident waves
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What happens when each point on the wavefront reaches the barrier?
It creates a wavelet moving away from the barrier, the wavelet lines up with the previous reflected wavelets to form a reflected wavefront moving away *
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What does this mean?
All parts of a wavefront move a the same speed so all reflected wavefront is at same angle to barrier as incident wavefront
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What do the reflected waves and the incident waves have the same of?
Same freq, wavelength and speed
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What is the image formed by a plane mirror?
Virtual ( same way up as the object, laterally inverted (back to front not upside down)
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When is a virtual image formed?
When light rays appear to come from after they have been reflected, can't be projected
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What is a real image?
An image that can be seen on a screen
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What is specular diffusion?
Diffusion from a smooth surface because parallel light waves are reflected in a single direction
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What is diffuse reflection?
Reflection in a rough surface
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Why does diffuse reflection happen?
Due to light being scattered in different directions
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What is refraction?
The change in direction of waves across a boundary from one medium to another
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When do light waves refract?
When they travel across a boundary between air and a transparent medium. This is because speed of light changes at this type of boundary
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What does light do when it travels from air to glass?
Bends towards the normal
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What does light do when it travels from glass to air?
Bends away from the normal
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Why do these changes happen?
Light travels more slowly in glass than air and glass is more optically dense than air
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What happens when light enters a more dense medium?
Refracted towards normal
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What happens when light enters a less dense medium?
Refracted away from medium
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How do colour filters work?
They absorb certain wavelengths and transmit others e.g. white light at red filter inky red light emitted because it absorbs all parts of white spectrum
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What are the primary colours of light? And why are they the primary colours?
Red, green and blue and because they can be mixed to produce any other colour of light
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What does the colour and surface of an opaque object depend on?
The chemicals (pigments) in the surface materials
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What does colour also depend upon?
The range of wavelengths in the incident light
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What does a white surface not have ?
Pigments
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What are transparent objects?
Objects that transmit all the incident light that hit object, none is absorbed
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What are translucent objects?
Objects that let light pass through but is scattered or refracted
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Why does this happen?
Material of object has lots of internal boundaries that change the direction of the light waves
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What is a convex lens? (Converging)
Makes parallel rays converge to a focus,
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What is the point called where parallel rays are focused to?
Principal focus
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What is a converging lens used for?
Magnifying glass e.g. distant objects in a camera
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What is a concave lens used for? (Diverging)
Makes parallel rays spread out
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What is a diverging lens used for?
Correcting short sight
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What is the distance from the centre of the lens to the principle focus called?
Focal length
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What happens if the image is bigger than the object?
The magnification is bigger than 1
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What happens if the image is smaller than the object?
The magnification is less than 1
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What image is formed by a convex lens?
A real image if the object is further away than the principal focus
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What image is formed by a convex lens?
A virtual image if object is nearer the principal focus
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Other cards in this set

Card 2

Front

It creates a wavelet moving away from the barrier, the wavelet lines up with the previous reflected wavelets to form a reflected wavefront moving away *

Back

What happens when each point on the wavefront reaches the barrier?

Card 3

Front

All parts of a wavefront move a the same speed so all reflected wavefront is at same angle to barrier as incident wavefront

Back

Preview of the back of card 3

Card 4

Front

Same freq, wavelength and speed

Back

Preview of the back of card 4

Card 5

Front

Virtual ( same way up as the object, laterally inverted (back to front not upside down)

Back

Preview of the back of card 5
View more cards

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