P3 Physics Revision

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  • Created by: amyclaire
  • Created on: 17-04-16 12:18
What is the function of the Cornea?
It is the front part of the eye with a tough coat, it is convex and transparent, refracting light, so it bends as it enters the eye
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What is the function of the Iris?
It is pigmented and decides the colour of your eyes, so light cannot pass through, its muscles contract and relax to alter the size of its central hole or pupil, controls how much light enters the pupil
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What is the function of the Lens?
It is transparent, bi convex flexible disc behind the iris attached by the suspensory ligaments to the ciliary muscles, it focuses light onto the retina
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What is the function of the Retina?
The lining of the back of the eye which contains rods, sensitive to dim light and black and white, and cones, sensitive to colour. A small area called the fovea in the middle of the retina has many more cones than rods. It contains light receptors
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What is the function of the Optic nerve?
It is a bundle of sensory neurones at the back which carry impulses from the eye to the brain
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What are the properties of X Rays?
Travel at speed of light, high energy, high frequency, short wavelength, cause ionisation, absorbed by dense materials e.g. bone
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What are some medical uses of X Rays?
Measuring bone density, examining dense materials e.g. bone, CAT scans give 3D images, highly focussed energy beams used ti kill cancer cells
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What are some precautions that can be taken?
Wearing a lead apron, limiting exposure, not having lots of X Rays
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How are X Rays produced?
Electrons from the hot cathode are fired at the tungsten target at high speed, when these high energy electrons strike the target, some of their energy is changed into X Rays
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When does total internal reflection occur?
When light is incident on a boundary between optically more to less dense substance (e.g. glass to air), and the angle of incidence is more than the critical angle,
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When does some reflection and some refraction occur?
When the angle of incidence is less than the critical angle
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When the angle of incidence is equal to the critical angle what happens?
Refraction at 90 degrees and partial reflection
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What image is formed by a diverging lens?
Virtual, diminished, upright
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Why would someone be long sighted/ hyperopia?
If the eye is shorter than normal, the image focuses behind the retina so doesn't focus when it reached the retina
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How can we correct long sightedness?
Using a convex lens, which focuses light in addition to the natural lens, onto the retina
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What is an astigmatism?
Eyestrain, headache, irregularly shaped cornea, shaped like rugby ball, not football, light focuses rays on 2 spots, not one as cornea has steeper and flatter curve, corrected with cylindrical curve in glasses lens
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What is myopia?
Short sightedness, eye is too long, image falls short of retina when object far, concave lens used to spread light out before it reaches the convex lens in the eye, letting image focus on the retina
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What are cataracts?
Lens is opaque, this causes blindness, the fibres clump to blur vision, can treat using new glasses and surgery
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What function in the eye has a similar function to the focusing screw in a camera?
The ciliary muscles which stretch or slacken the suspensory ligaments to adjust the shape of the lens
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What function in the eye has a similar function to the aperture in a camera?
Iris
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What function in the eye has a similar function to the photosensitive surface in a camera?
Retina, detects light, converts light into electrical impulses
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What happens if the line of action of the weight of a body lies outside the base of the body?
There will be a resultant moment and the body will tend to topple
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When a body moves in a circle it continuously...?
accelerates towards the centre of the circle, this acceleration changes the direction of motion of the body not its speed, the resultant force causing this acceleration is called the centripetal force
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What is an electromagnet?
It is made of a coil of insulated wire wrapped around an iron core, with electric current flowing through it.
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In Flemings Left Hand rule, what does each finger mean?
Thumb- movement, Forefinger- field, Second finger- current
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What is the motor effect?
The force felt by a wire that has current flowing through it when it is placed perpendicularly in a magnetic field
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What happens if a wire cuts through magnetic field lines?
An electrical potential difference is induced across the ends of the conductor. If the wire is part of a complete circuit a current is induced in the wire
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When is the size of the induced potential difference increased?
When the speed of the movement increases, the strength of the magnetic field increases, the number of turns on the coil increases, the area of the coil is greater
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If a conductor parallel to an ammeter moves parallel to the lines of a magnetic field, what happens?
No current passes through the ammeter
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Other cards in this set

Card 2

Front

What is the function of the Iris?

Back

It is pigmented and decides the colour of your eyes, so light cannot pass through, its muscles contract and relax to alter the size of its central hole or pupil, controls how much light enters the pupil

Card 3

Front

What is the function of the Lens?

Back

Preview of the front of card 3

Card 4

Front

What is the function of the Retina?

Back

Preview of the front of card 4

Card 5

Front

What is the function of the Optic nerve?

Back

Preview of the front of card 5
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