• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4

# Light notes

Extracts from this document...

Introduction

LIGHT and OPTICS SUMMARY

Light and Vision

Light follows the same path when travelling in either direction.

Light follows the path that will get it between two points in the shortest time.

Light travels fastest in a vacuum 3.0 x 108 m/s and in straight lines through a uniform medium.

You can't see light just the object, if light leaves it and then enters the eyes.

Objects are where they are seen to be if the light travels fast in straight lines.

Light changes speed and direction when it passes into a different substance. This is refraction.

If light changes direction between leaving an object and entering the eyes, the object will seem to be directly back along the last straight path the light followed.

The size of the angle subtended at the eye by the object controls how big the object seems to be.

Light travels as a wave. The frequency of the wave is the number of vibrations per second.

Light has a range of frequencies  Your eyes can sense which frequencies have entered and your brain gives you the sensation of colour.

The colours of the complete spectrum are red, orange, yellow, green, blue, indigo and violet.

The atoms in an object control which frequencies are absorbed and which are reflected.

Middle

An object inside the focus has a virtual image because light does not pass through the place where the image is formed. Reflected light seems to have come from behind the mirror in straight lines.

Virtual  images formed by concave mirrors are upright, enlarged and seem to be behind the mirror.

The virtual image can only be seen by looking into the mirror.

Used as the collector of light in big telescopes or by a dentist as a magnifier or a tooth.

Convex Mirrors

Light paths parallel to the axis reflect and diverge as if all coming from a point behind the mirror - the focus.

The distance from the focus to the centre of the mirror is the focal length.

The more curved the mirror, the shorter the focal length.

All objects regardless of distance have images that are virtual, upright, diminished that form behind the mirror between the mirror and the focus.

The virtual image can only be seen by looking into the mirror.

If the object is at infinity - a few metres, the image is formed at the focus.

Used where vision is restricted - the image seen in the mirror is of a wide area infront of the mirror.

Refraction

Conclusion

The shorter the focal length of the lens, the wider the field of view.

The depth of field is the distance between the objects closest and furthest from the camera that are in acceptable focus for one position of the lens.

The greater the focal ratio, the greater the depth of field.

The exposure time is the time the image falls on the film while the shutter is open.

The ASA of a film is 1 over the exposure time needed to take a good picture in bright sunshine when the focal ratio is 16.

The bigger the ASA rating of a film, the less light is needed to take a good picture.

Colour Photography

Films and prints have layers sensitive to red, green and blue light.

After developing the film or print, coloured dyes appear in the layers where these types of light were absorbed.

A magenta dye is in the green sensitive layer where green light was absorbed, a cyan dye is in the red sensitive layer where red light was absorbed, a yellow dye is in the blue sensitive layer where blue light was absorbed.

The dyes form filters. A magenta and yellow combination allows red light through, a magenta and cyan combination allows blue light through and a cyan and yellow combination allows green light through.

The colour that appears on the negative is the complimentary colour in the original scene.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related AS and A Level Electrical & Thermal Physics essays

1. ## Using an LDR to detect the intensity of plane polarised light allowed through a ...

to suggest that the intensity of light emitted from a 60W bulb is approximately 50 lux. Therefore, the intensity that I would be interested in is the value of resistance from 25 lux downwards. This graph, from https://wwws.ee.ucl.ac.uk/facilities/teachlab/info/data/ldr seems to indicate that the resistance in the values that I need will be between 10 and 0.1 k??

2. ## Light and matter notes

- show constructive and destructive interference when light paths overlap. - cause coloured effects and is due to a difference in the frequency of the waves. - be able to be polarized. The wave model has difficulty explaining: - the increase in the angle of refraction when the frequency of the light increases.

1. ## Light intensity notes

Which is an utter nonsense. It is thought that dark matter could be the missing piece that would solve this conflict. Obviously its` presence would change the rate of recession of galaxies due to gravity. Cosmological Red-Shift As light travels from one galaxy to another, the universe expands, which stretches the wavelength of the light (or other radiation).

2. ## Choosing a light source

discharge tube similar to neon signs and mercury or sodium Vapor Street. Light is produced when pair of electrodes, one from each end is sealed along with a drop of mercury and some inert gases (it's usually argon) at a very low pressure inside a glass tube.

1. ## PID Control Case Study - Balanced beam demonstration

the requirement to provide enough current to actually balance the beam for a given weight. Thus, the only design variable left is d, the differential gain. By measuring K of the system, which was around 80s-2 (Diag.9, Section 4.0), the optimum value of d was found by simulation to be around 0.8 seconds.

2. ## Electro-Static Revision Notes.

Force inversely proportional to square of separation of charges - Force inversely proportional to square of separation of masses. Electric field round a charge - Gravitational field round a mass.

1. ## Current rating of fuses and MCB's.

In this practical the fusing factor was . This value is rather high. However the value might not be the exact fusing factor of the fuse used due to the errors that are present in the practical. MCBS Circuit symbol: The MCB has several advantages over fuses which have been

2. ## Build a successful sensor that will measure the proximity of a light source.

calculated at any given distance from the photodiode, using any relationship found between the resistance and the distance from light, e.g. Light intensity. The above formula relates directly to Ohm's law. Ohm's law states that 'Conductance or resistance can be calculated at any given current or voltage.

• Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to