Specular reflection is reflection from smooth surfaces in one direction.

Diffuse reflection is reflection from rough surfaces in multiple directions.

A ray is a straight line drawn to represent the direction that a light wave travels.

The normal is an imaginary line drawn at 90° to a surface.

Wavefronts are lines drawn to represent peaks of a wave.

Reflection of light (including specular and diffuse)

Physics

Refraction through a rectangular block

Refraction through a semicircular block

Light and colour

Convex lenses

Scale diagrams for convex lenses

Virtual images from convex and concave lenses

The spectrum of electromagnetic waves

Absorbing infrared radiation practical

Emitting infrared and black body radiation

Ionising electromagnetic radiation

Non-ionising electromagnetic radiation

In A-level physics, some pupils will build on this knowledge to learn about the photon model of electromagnetic radiation and the use of electromagnetic radiation for collecting evidence about the universe or for generating images of the inside of a human body.

In the Measuring waves unit, pupils learnt about the measurable features of a wave, the relationship between them and the wave equation.

This unit explores reflection, refraction, and lenses using ray diagrams. It covers the electromagnetic spectrum, light as a wave, absorption, transmission, and practical uses. Emphasis is on risks, temperature balance, data presentation, and unit conversions.

Electromagnetic waves

Refraction occurs when waves travel from one transparent medium to another, causing a change in wave speed and direction.

The angle of incidence is the angle between the incident ray and the normal.

The angle of refraction is the angle between the refracted ray and the normal.

Refraction occurs when waves travel from one transparent medium to another, causing a change in direction.

A medium is the material through which a wave is travelling.

Total internal reflection is when waves fully reflect from a boundary to a medium when greater wave speed, rather than being transmitted through.

Electromagnetic waves are ripples/oscillations in the invisible electric and magnetic fields that are all around us.

The frequency of a wave is the number of oscillations that occur per second.

The wavelength of a wave is the distance between one point on a wave and the same point on the next wave.

Waves are said to refract when they change direction upon entering a new medium.

An object is opaque if no light is transmitted through it.

Diminished means smaller than an object’s real size. It is the opposite of magnified.

A convex shape bulges ‘out’ rather than bulging ‘in’ (concave).

Rays of light incident on a convex lens parallel to the principal axis are focused to a point called the principal focus.

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

The greater the power of a lens, the greater the angles through which light is refracted and the shorter the focal length.

The object distance is the distance between an object and a lens.

The image distance is the distance between a lens and an image formed by that lens.

The principal focus is the point to which parallel rays (from distant objects) are focused.

The focal length is the distance between the centre of a lens and the principal focus.

The principal axis is a line through the centre of a lens, 90° to the optical axis of the lens.

The principal focus for a convex lens is the point to which rays parallel to the principal axis are focused. For a concave lens it is the point from which such rays appear to be diverged.

When rays of light are brought to a focus a real image forms. A real image can be projected onto a screen.

Virtual images occur at points where rays appear to (but do not actually) originate from. They cannot form on a screen.

Virtual rays are dashed lines drawn to represent where rays of light appear to have come from.

Electromagnetic waves are oscillations/ripples in electric and magnetic fields.

The frequency of a wave gives the number of oscillations that occur per second.

A spectrum is a continuous range or scale.

Refraction is when waves enter a new material and change direction.

Anything that is emitted (given out) from a system and transfers energy away from that system can be called radiation.

Absorption is when an electromagnetic wave is incident on a surface and transfers some or all of its energy to that surface.

Infrared radiation means electromagnetic waves with frequencies in a range just lower than for red light.

Electromagnetic waves are oscillations (ripples) in electric and magnetic fields.

The frequency of a wave is the number of oscillations that occur each second.

Control variables are variables that must remain the same throughout an investigation.

To emit infrared radiation is to give out infrared radiation.

The temperature of an object measures how hot or cold it is.

A Leslie cube is a hollow metal cube that can be filled with hot water. Each side has a different colour and finish so emits different intensities of infrared radiation.

A black body is a theoretical object that absorbs all of the radiation that falls on it.

Electromagnetic waves transfer energy because stores of energy decrease when they are emitted and increase when they are absorbed.

Ionisation is the process of an atom losing or gaining electrons so become charged/becoming an ion.

Ultraviolet means EM radiation with frequencies greater than visible light but lower than X–rays.

X-rays are EM radiation with frequencies greater than ultraviolet but lower than gamma rays.

Gamma rays are the highest frequency electromagnetic waves.

The frequency of a wave means the number of oscillations occurring per second, which is the same as the number of waves arriving per second.

Radio waves, microwaves, infrared and visible light are non–ionising electromagnetic waves, as they cannot remove electrons from atoms.

Any process that transfers energy because of a temperature difference, or causes a temperature rise, can be called heating.

An antenna is a metal structure designed to emit or absorb electromagnetic waves.

Electromagnetic waves

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