Wavefronts are lines of disturbance which pass through a material.
1 of 28
What happens when the radius of wavefronts increases.
As the radius increases, curvature reaches zero. Wavefronts become plane wavefronts.
2 of 28
What do converging lenses do?
A converging lens focuses light at high intensity on the focus. The lens bends plane wave fronts from the sun into spherical ripples that converge. Distance from lens to focus is radius of wavefronts after passing lens.
3 of 28
What happens to images when they pass a converging lens?
The converging lens makes an image upside down as the top of the object is focused at the bottom.
4 of 28
What is the formula to find the focal length?
1/v=1/u+1/f where u is written as negative.
5 of 28
What do objects at varying distances produce from the lens?
Distance light produces an image at focus. Nearby object beyond focus produces image at image distance. Object at focus produces very distant image.
6 of 28
What practical finds power and focal length of converging lens?
A small filament lamp is the object which an opaque screen for the lens to project the image. Change object distance u and measure v. Use intercept of 1/v or 1/u to find 1/f.
7 of 28
When is magnification negative?
Magnification is negative when image is upside down.
8 of 28
What's the magnification formula?
Linear magnification = image height/object height = v/u
9 of 28
What do CCDs do?
Image from lens is focused onto a CCD covered by pixels which store electric charge. More light=more charge.
10 of 28
How do CCDs use binary?
On = high PD=1, off=low PD=0. Pixels have 256 shades of grey. One value = a bit.
11 of 28
How many bits make a byte?
A group of 8 bits is a byte.
12 of 28
What formula connects N and B?
N=2^b where b is bits and N is number of arrangements.
13 of 28
What is resolution?
Resolution is the scale of the smallest detail distinguished. Resolution = Distance/pixels.
14 of 28
What is the information formula?
Information = no of pixels * bits per pixel.
15 of 28
What is the range of pixels?
8 bits is coded by pixels numbered 0-255.
16 of 28
How is brightness increased, and how is noise removed?
Change brightness - increase brightness until brightest pixel is 255. Removing noise - use mean smoothing to reduce random speckles.
17 of 28
What is edge detection?
Enhance edges, subtract average value of neigbours from each pixel to remove uniform areas of brightness and pick areas where it changes quickly.
18 of 28
How is contrast changed?
Changing contrast, stretch range from 0-255
19 of 28
What is the wave formula?
c = frequency * wavelength. Higher speed has a longer wavelength.
20 of 28
What relates all EM waves?
All EM waves are transverse and travel at speed c.
21 of 28
What are wavelengths for radiowaves, microwaves, and infrared?
Radio waves 10^6-10^-1m. Microwaves: 10^-1-10^-3m. Infrared - 10^-3-7*10^-7m
EM waves vibrate with electric and magnetic fields vibrating perpendicular to each other. If a wave is polarised the direction of oscillation is fixed as opposed to randomly changing in all planes.
24 of 28
What do polarising filters show?
If unpolarised light passes a polarising filter, this polarises light. If the filter is rotated and light intensity is constant, light is unpolarised.
25 of 28
How is polarisation of radio waves found?
Radio wave receiving aerials can be rotated perpendicular to direction of waves. When parallel to polarisation plane intensity is max.
26 of 28
How is polarisation shown in a tank?
Shine light through milky water in a tank. Above water, rotate polarising filter. No vibration in vertical plane. Same effect horizontal.
27 of 28
How is polarisation of microwaves found?
A transmitter emits polarised microwaves. Rotate metal grille. Strength of signal at receiver changes.
28 of 28
Other cards in this set
Card 2
Front
What happens when the radius of wavefronts increases.
Back
As the radius increases, curvature reaches zero. Wavefronts become plane wavefronts.
Card 3
Front
What do converging lenses do?
Back
Card 4
Front
What happens to images when they pass a converging lens?
Comments
No comments have yet been made