GCSE AQA Physics - Unit 3


Get ready for the final chapter in the epic GCSE AQA Physics trilogy. The Sun has hit its White Dwarf stage, Lord Nova has won. Now Dr.Physics must bring his band back together for one final battle to save Physika! Friendship dies and true love lies, night will fall and the dark will rise, as a good physicist goes to war...
James Jolliffe
Flashcards by James Jolliffe, updated more than 1 year ago
James Jolliffe
Created by James Jolliffe over 8 years ago

Resource summary

Question Answer
Fill in the missing words: X-rays form part of the ________________ _____________. They have _____ wavelengths and can cause _____________. Electromagnetic Spectrum Short Ionisation
Is an X-ray a transverse wave or a longitudinal wave? Transverse wave
What are the advantages of X-Rays? X-Rays are transmitted by healthy tissue. X-Rays are absorbed by metal and bone to produce shadow pictures.
What can X-rays be detected with to form an image electronically? Charge-Coupled devices
Ultrasounds are sound waves of frequencies greater than... 20 000Hz.
Is an ultrasound wave a transverse wave or a longitudinal wave? Longitudinal wave
Give some examples of the use of Ultrasound in medicine. - Pre-natal scanning. - Imaging of damaged ligaments and muscles. - Imaging of kidneys and destruction of kidney stones.
What is reflection? When light changes direction as it hits a surface.
What is refraction? When light crosses an interface (a boundary between two transparent media of different densities) and it changes direction.
What is the refractive index? The degree to which a material slows the speed of light.
What are the two main types of lenses, and what are their features? Converging Lens (convex lens) - Thickest at the centre. Diverging Lens (concave lens) - Thinnest in the centre.
Fill in the missing words: A light ray that enters a lens at its centre is ______________. This is called the ____________ ______ of the lens. Undeviated Principal Axis
What is the focal length (f)? The distance between the centre of the lens and the focus (real or virtual)
The image produced by a convex lens is... - Real (on the other side of the lens) - Inverted - Smaller (for distant objects) or Magnified (for closer objects)
The image produced by a concave lens is... - Virtual (on the same side as he object) - Upright (not inverted)
How can you work out the magnification of a lens? Magnification = Image Height / Object Height
Fill in the missing gaps: For a given focal length, the greater the refractive index, the _________ the lens (i.e. _________). Flatter Thinner
The Eye - Fill in the missing gaps - Part 1: The ________ refracts most of the light whilst the _______ (opening in the ______) adjusts the light intensity. Cornea Pupil Iris
The Eye - Fill in the missing gaps - Part 2: The _____ provides further refraction before the image is formed on the light-sensitive ________. The _______ _______ carries this information to the brain. Lens Retina Optic Nerve
What muscles control the shape of the eye lens? Ciliary Muscles
Label this picture of an eye:
What are the two types of defective vision, and what are they caused by? Long sight - caused by the eyeball being too short and unable to focus on near objects. Short sight - caused by the eyeball being too long and unable to focus on distant objects.
In a magnifying glass, the image is... virtual, upright and enlarged.
Fill in the missing gaps: As ultrasonic waves pass from one ________ or ___________ into another, they are __________ ___________ at the ___________. Medium Substance Partially Reflected Boundary
What are the two special cases involving the refraction of light? 1. The angle of refraction is equal to 90°, the light ray travels on the boundary between between glass and air. The angle of incidence is then called the critical angle (c). 2. The angle of incidence is greater than the critical angle. In this case total internal reflection takes place. No refraction occurs so no light escapes from the glass.
What is a laser (apart from a really cool thing that shoots aliens)? A device that amplifies light to produce a very intense and very narrow beam.
When are lasers used in eye surgery? - To repair damaged retinas - To remove diseased or damaged cells by cutting, cauterising or burning the tissue.
What is the centre of mass (C of M) of an object? The point through which the whole mass of the object is considered to act. It can be thought of as the point where all the mass is concentrated.
What is the frequency of oscillation? The number of times the mass of a pendulum swings back and forth every second.
What is a moment? The turning effect of a force around a fixed point called a pivot.
What two things can you do to increase the size of the moment? - Increase the value of the force. - Increase the perpendicular distance.
What is a lever? A device that acts like a force multiplier or a distance multiplier.
Give two examples of the application of levers: - Lifting a wheelbarrow. - Opening a tin of paint with a screwdriver.
When an object isn't turning, there must be a balance between... The total moments of the forces turning the object in a clockwise and anticlockwise direction.
What is the last answer known as? The law of moments.
Why would an object topple over? If the line of action of the force (e.g. its weight) lies outside its base. The weight of the object causes a turning effect, which makes the object topple.
What is pressure? The force that acts over a particular surface area.
Fill in the missing gaps: Liquids are virtually ________________, and the ____________ in a liquid is transmitted ___________ in all directions. Incompressible Pressure Equally
The pressure in a liquid can be used to work machinery and is known as... hydraulics.
Fill in the missing words: Any object moving with a constant speed in a _________ path is ______________ _____________ towards the centre of the circle. Circular Continuously accelerating
What is the centripetal force? The force that acts on a body moving in a circular path and is directed towards the centre which the body is moving.
An increased radius will __crease the centripetal force. An increased mass/velocity will __crease the centripetal force. De(crease) In(crease)
What provides the centripetal force when a car goes round a bend? The tyres
Fill in the missing gaps; when a current flows through a wire a ___________ _______ is produced around the wire. Magnetic field
What is the right-hand rule.
What is the motor effect? The force a current-carrying wire experiences when placed in a magnetic field.
What is Fleming's Left-hand Rule used to identify? The direction of the force (from the motor effect).
Fleming's Left-hand Rule: The first finger points in the direction of the ____________ _______. The second finger points in the direction of the ____________. The thumb points in the direction of the _____________. Magnetic Field Current Movement
Put your hand in Fleming's left-hand Rule position. It should look like this...
Fill in the missing gaps: Electromagnetic induction uses ___________ to produce a __________. Movement Current
What happens if a conducting wire, or coil of wires is moved though or 'cuts' through a magnetic field? A potential difference (p.d.) is induced across the ends of the wire.
What would happen then if the coil of wire formed part of a complete circuit? An electrical current would be induced.
Induced currents are used in a bicycle... dynamo.
How can the size of the potential difference (p.d.), and hence the current, be increased? - Increasing the speed of the movement of the magnet or coils. - Increasing the strength of the magnetic field. - Increasing the number of turns on the coil.
What do transformers do? A transformer changes electrical energy from one potential difference to another potential difference.
What are transformers made up of? Two coils, called the primary and secondary coils, wrapped around a soft iron core.
How does an alternating current flowing through the primary coil of the transformer create an alternating current in the secondary coil? The alternating current creates a changing/alternating magnetic field in the iron core, causing a potential difference to be induced in/across secondary coil.
The potential difference across the primary and secondary coils of a transformer are related by the equation... Vp/Vs = Np/Ns Vp = Potential difference across the primary coil in Volts. Vs = Potential difference across the secondary coil in Volts. Np = Number of turns on the primary coil. Ns = Number of turns on the secondary coil.
A step-up transformer has ____ turns in the secondary coil than the primary coil. The potential difference across the secondary coil is ________ than that across the primary coil. More Greater
A step-down transformer has _____ turns in the secondary coil than the primary coil. The potential difference across the secondary coil is ________ than that across the primary coil. Fewer Less
Switch mode transformers are much _________ and __________ than traditional transformers and operate at a much ________ frequency, often between __kHz and ___kHz. Lighter (and) smaller Higher 50(kHz and) 200(kHz)
Give some examples of the application of switch mode transformers... Mobile Phones Digital Cameras Laptops
What is 1 second in 'µs' (Used for ultrasound calculations) 1 second = 1 000 000 µs
Why do x-rays provide a better quality of image than ultrasound? They have a shorter wavelength.
What is the power of a lens measured in? Dioptres (D)
What is the focal length measured in? metres
For a lens, the greater the refractive index... the flatter it can be.
What is the shape of the eye lens like when focusing on near objects? Fat, more curved
What is the shape of the eye lens like when focusing on distant objects? Thin, less curved
What are the three factors affecting the centripetal force? The mass of the object The speed of the object The radius of the circle in which it is travelling
How can you increase the centripetal force? Increase the: Mass, Speed OR Radius of circle in which it is travelling.
What is pressure measured in? Pascals (Pa)
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