Light & Waves Flashcards
Wave
Transfer of energy but not matter
Transverse Wave
Oscillations are perpendicular to the transfer of energy
- S waves
- light
Longitudinal Wave
Oscillations are parallel to the direction of energy transfer
- P waves
- sound
Wavelength λ
The shortest distance between two points on a wave that are in phase
Frequency
The number of oscillations per second (Hz)
Time Period
The time taken for one oscillation (s)
Peak
The maximum positive displacement of a wave
Trough
The maximum negative displacement of a wave
Equilibrium Position
The rest position of the medium if there wasn’t a wave moving through it
Amplitude
The maximum displacement of a wave
Displacement
The distance a point is from the equilibrium
Wavefront
A line representing the points on a wave that are all in phase and the same distance from the source of the wave
In Phase
Waves that have identical physical properties
- speed
- velocity
- displacement
- acceleration
Anti-phase
When points on a wave has opposite physical properties
Transmission
When a wave passes through a material
Absorption
When a wave’s energy is transferred to the material it passes through
Reflection
When a wave bounces off an interface between two different media, back to its original medium
Specular Reflection
Waves reflecting parallel to each other off a smooth surface
Diffuse Reflection
Waves reflecting off an irregular surface in random directions
Diffuse Reflection
Waves reflecting off an irregular surface in random directions
Primary Colours
Red
Blue
Green
Secondary Colours
Magenta
Cyan
Yellow
White Light
Contains all colours on the spectrum
Mixing all three primary colours produces white light
Filter
Absorbs some colours and allows other colours to transfer through the filter
magenta object + red filter = blue object
red object + red filter = black object
Speed of Light
3 x10⁸ m/s
Refraction
When light enters a medium of different density and changes speed. The change in speed causes the ray to bend. The wavelength changes but frequency always stays the same
Incident Ray
The ray of light entering the new medium
Refracted Ray
The ray of light that gets bent in the second medium
Emergent Ray
The ray of light that leaves the second medium and returns to it’s original velocity
Angle of Incidence
The angle from the normal to the ray of incidence
Angle of Refraction
The angle from the normal to the refracted ray
Critical Angle
The angle from the normal to the incident ray when the refracted ray is parallel to the surface of the medium
Total Internal Reflection
When the angle of incidence is greater than the critical angle, all of the light is reflected back
Fibre Optic Cables
Thin glass cables that transmit binary values in pulses of light using total internal reflection
Convex Lens
(Converging lens) Outwards bend
Parallel rays of light that are parallel to the principal axis will refract inwards and converge at the focal point
Concave Lens
(Diverging lens) Inward bend
Parallel rays of light will refract away from each other. Adding virtual rays to the diagram show the rays crossing at the nearside focal point
Virtual Images
When real rays do not meet. Virtual rays can be drawn to form a virtual image. They cannot be projected onto a screen. Mirrors
Real Images
When real rays meet to form a real image. They can be projected onto a screen
Power of a Lens
P = 1/focal length
measured in dioptres
Focal Length
The distance between the (optical) centre of the lens to the focal point
Magnified
When the image is bigger than the object
Diminished
When the image is smaller than the object
Magnification
image height / object height
S Waves
- Transverse
- Only travel through solids → shadow zone
- Slower but more destructive (oscillate perpendicularly to energy transfer)
P Waves
- Longitudinal
- Travel through solids + liquids
- Faster but less destructive
