Properties of waves, including sound and light Flashcards
What is a ‘Ripple tank’ [2]
Shallow glass-bottomed tank containing a small amount of water. Light from above, shining through the water creating a shadow of the ripples on the floor below, showing the pattern in which the ripples form
Ripples are produced by… [1]
by something that moves up and down (vertically, usually wooden bars) but the ripples move out horizontally
define ‘waves’ [1]
Disturbance in medium that transports energy and momentum
define ‘wavelength’ [1]
distance from one crest to another or from one trough to another, measures in metres
define ‘Amplitude’ (A) [1]
The maximum distance that the surface of the water is displaced from its undisturbed level (or) the height of the crest (M)
define ‘Frequency’ (f) [1]
The number of waves per second passing a point. (Hz)
1Hz=1 wave or ripple per second
define ‘Period’ (T) [1]
A wave is the time taken for one complete wave to pass a point. (s) crest to crest
F=1/T or T=1/f
what is wave speed? [1]
The speed at which it transfers energy from one place to another.
what are transverse waves? [1]
Waves in which particles carrying the wave move from side to side, perpendicular to the direction in which the wave is moving (E.g. light)
what are longnitude waves? [1]
Waves in which the particles carrying the wave back and forth, along the direction in which the wave is moving (E.g. sound)
what is compression? [1]
areas of the sound waves where the air particles are closer together and the air is dense
what is ‘rarefaction’? [1]
areas of the sound wave where the particles are farther from each other and the density of the air is less
Mechanical waves need… [1]
a medium
(non-mechanical do not)
When waves enter on medium from another… [1]
The wavelength and velocity keep changing but the frequency remains constant
what is a wavefront [1]
a surface containing points affected the same way by a wave in a given time. The separation of the wavefronts of the ripples is equal to their wavelength
Refraction occurs when… [1]
The speed of light changes when it is travelling from one medium to another
Diffraction occurs when… [1]
ripples in the water encounter a slit/opening in a barrier and they spread out into the space beyond the barrier. When the width of the gap is equal to the wavelength, diffraction is the greatest
What is the speed of sound in air? [1]
33m/s or 1200 km/h
travels 1 km in 3s
what is an echo? [1]
Reflection of sound when it hits a hard surface and reflects
a higher pitch is due to… [1]
a higher frequency
define ‘sound’ [1]
vibrations that travel through air and other mediums and are produced by vibrating objects
what is the speed of light? [1]
3 * 10^8 m/s
Reflection occurs when… [1]
a Light ray strikes a shiny surface and bounces back in a straight line. The angle of incidence is equal to the angle of reflection
what is considered a real image? [1]
the image which can be captured/formed on a screen
what is considered a virtual image? [1]
an image which can’t be caught/captured on a screen
an object reflected on a plane mirror is… [4]
The same size as the object, left-right inverted,
virtual,
same distance behind mirror as object is in front
Refraction is.. [3]
bending of light rays when they enter one medium from another, due to change in speed.
2 laws:
1. incident ray, ratio of sin of angle of incidence to sin of angle of refraction is constant for a pair of media
- If light is perpendicular (90 degrees) to the medium it is entering, refraction doesn’t take place
what is a refractive index? [1]
the quantity that tells us by how much light slows down while entering a particular media.
n = [2]
n = speed of light in vacuum (3*10^8) / speed of light in the material
what is Snells law? [1]
sin of angle of incidence with the angle of refraction and also the refractive index, because as the refractive index increases, so does the ray’s bending.
what is a critical angle?
the angle of incidence in the denser medium for when angle of refraction is 90 degrees or more
what is the principal axis? [1]
horizontal line passing through the centre of the lens
