Waves ( light and sound) Flashcards
Topic 2 D
light waves are what type of waves
transverse waves
can light waves be refracted
yes
can light waves be reflected
yes
what is the law of reflection
angle of incidence = angle of reflection
properties of mirror images (4)
- upright
- same size as objects
- laterally inverted
- virtual ( can’t be projected on a screen)
frequency range for humans
20 - 20000 Hz
sound waves are what type of wave
longitudinal
reflection of a sound wave is called an
echo
sound can undergo
reflection and refraction
what waves can be reflected or refracted
all waves
reflection happens when
A wave hits a boundary between two media and does not pass through, but instead stays in the original medium
refraction happens when
A wave passes a boundary between two different transparent media and undergoes a change in direction
An incident ray has an arrow pointing towards or away from the boundary ?
towards
A reflected ray has an arrow pointing towards or away from the boundary?
away
The change in direction of the refracted ray depends on the difference in ____ between the 2 mediums
density
in refraction, From less dense to more dense (e.g air to glass), light bends to/away the normal
towards
in refraction, From more dense to less dense (e.g. glass to air), light bends away/to from the normal
away
When passing along the normal (perpendicular) the light does or doesn’t bend
doesn’t
When light passes into a denser substance the rays will slow down, so rays will bend towards/away normal
towards
The only properties that change during refraction are (2)
speed and wavelength
does frequency change during refraction
no
does light change colour when it refracts
no
INVESTIGATION REFRACTION PRACTICAL
Place the glass block on a sheet of paper, and carefully draw around the rectangular perspex block using a pencil
Switch on the ray box and direct a beam of light at the side face of the block
Mark on the paper:
A point on the ray close to the ray box
The point where the ray enters the block
The point where the ray exits the block
A point on the exit light ray which is a distance of about 5 cm away from the block
Draw a dashed line normal (at right angles) to the outline of the block where the points are
Remove the block and join the points marked with three straight lines
Replace the block within its outline and repeat the above process for a ray striking the block at a different angle
Repeat the procedure for each shape of perspex block (prism and semi-circular)
what is snells law
n = sin i
——
sin r