Waves and optics Flashcards
Label the diagram of the wave: amplitude, peak, wavelength, peak, trough
What does a wave transfer
Energy without transferring matter
What is the wavelength of a wave
- The distance from a point on one wave to the same point on the next wave
- Usually measured from the peak of the wave
What is the amplitude of a wave
- The height of the wave, measured from its middle to the top
What is the frequency of a wave
- The number of waves passing a point every second
What is the unit of frequency
hertz (Hz)
How do the points vibrate in a transverse wave
The points along the wave vibrate at 90 degrees to the direction in which the wave is moving
How do the points vibrate in a longitudinal wave
The points along the wave vibrate in the same direction that the wave is moving in
example of longitudinal wave
sound waves
Example of a transverse wave
light waves
What is the equation for wave speed including wave speed, frequency and wavelength
- wave speed = Frequency x wave length
- v = f x l
- m/s = Hz x metres
What happens when a wave reflects of a plane surface
Angle of incidence = angle of reflection
How can a wave undergo refraction
- When a wave enters a different medium it changes speed, this is called refraction
- Refraction causes wavelength to increase or decrease
- And cause a change in direction
What happens when water goes from shallow to deep water
The waves speed up
What happens to the wavelength when waves speed up
The waves spread out
- When slowing down they bunch together
What is diffraction of a wave
- When waves pass through a narrow gap, the waves spread out, this is called diffraction
What happens to a wave with a small gap in diffraction
What happens to a wave in a larger gap in diffraction
What happens in diffraction around an edge
When an object is placed in front of a mirror, what are its characteristics
- The image is the same size as the object
- The image is as far behind the mirror as the object is in front
- It is directly in line with the object
Draw out an example of a virtual image in a mirror
How is a virtual image formed
It is formed from the divergance of rays from the image
What phrase describe the travel of light in refraction
- Enters towards (the medium)
- Leaves away (from the medium
What is the critical angle
the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.
What is the equation for the refractive index involving angle of incidence, angle of reflection, refractive index
n = sin(i) / sin(r)
What is the equation for a refractive index involved refractive index, speed of light in vacuum and speed of light in material
n = speed of light in vacuum / speed of light in material
n = 1/sinC
When does internal reflection occur
when light moves from a denser medium to a less dense one
Conditions for total internal reflection to occur
- Light is travelling from a more dense to less dense medium
- The angle of incidence must be greater than the critical angle
What is a real world use of internal reflection
Optical fibres in medicine and communications
How do optical fibres work
Light travelling down the fibres is reflected each time it hits the wall of the fibre
what are the steps to form a real image
- Draw a line directly through the centre of the lens from the top of the object
- Draw a line straight across from the top of the object
- Once it reaches the centre line of the converging lens, it then travels towards the principal focus
How does dispersion occur
- White light enters a denser medium
- The colours which make up white light refract at different rates
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Which colour in light has the longest and shortest wavelength
- Red has the largest
- Violet has the shortest
