carriers of energy

• identify, with the use of examples the transfer of energy by waves

  • mechanical (sound waves, earthquake and surface water waves)

  • electromagnetic (radio, x-rays, gamma rays and visible light)

• compare longitudinal (compression) waves and transverse waves

  • longitudinal waves’ medium moves in the same direction as the wave, and the movement of the particles of from left to right and forces other particles to vibrate.

  • in a transverse wave the medium moves perpendicular to the direction of the wave, the particles also move up and down as the wave moves horizontally.

• recognise the difference between mechanical and electromagnetic waves

  • mechanical waves require a medium (a substance or material that carries a wave) to propagate

  • electromagnetic waves do not require a medium to spread

• describe frequency

  • the number of complete wave cycles that pass a given point in a certain amount of time, measured in hertz

• describe period (T)

  • the amount of time it takes to complete one cycle

• describe wavelength

  • the distance from crest to crest or from one trough to trough

• state the equation for speed

  • speed= wavelength x frequency

  • v=  λ x f

• examine how sound waves pass through the ear to allow us to hear

  • sound waves enter the outer ear and travel through the ear canal, leading to the eardrum. The eardrum then vibrates from the incoming sound waves and sends these vibrations to three tiny bones in the middle ear.

• is visible light a form of electromagnetic radiation?

  • yes, all electromagnetic radiation is light

• recall the different electromagnetic waves

  • radio

  • microwave

  • infrared

  • x- ray

  • ultraviolet

  • gamma ray

  • visible light

• identify the properties and uses of electromagnetic waves

  • properties: wavelength, frequency and speed

  • they can propagate through vacuum and mediums

  • they can be absorbed, reflected, refracted or transmitted by matter

• describe the reflection of light from plane and curved mirrors and identify some useful applications

  • mirrors can be flat or curved.

  • flat mirrors= used in bathrooms and cars

  • curved mirrors= used in security cameras, they an make things look bigger or smaller

• explain how images are formed when light passes from one medium to another of different optical density

  • When light passes from one medium to another with a different optical density, it bends. This is called refraction. The bending of light causes the image to appear in a different position than its actual location. The amount of bending depends on the angle of incidence and the refractive indices of the two media.

• outline everyday instances in which refraction is evident

  • a spoon appearing bent when placed in a glass of water

  • a rainbow formed by sunlight refracting through water droplets

• distinguish between reflection and refraction

  • reflection= light bounces back from a surface

  • refraction= light bends as it passes from one medium to another

• describe the different types of lenses and how they work to focus light

  • convex lenses= thicker in the middle than at the edges. they converge parallel light rays to a focal point

  • concave= thinner in the middle than the edges. they diverge parallel light rays

• identify applications of lenses

  • cameras

  • telescopes

  • microscopes

  • eyeglasses

  colour and vision

• recall how the eye functions to provide vision

  • the eye works by focusing light on the retina, where photoreceptor cells (rods and cones) convert light into electrical signals that are sent to the brain

• account for the colour of objects in terms of absorption, transmission and reflection of the colour spectrum

  • the colour of objects depends on the wavelengths of light it absorbs and reflects

  • (e.g. a red object reflects red light and absorbs other colours)

• outline the function of the retina in relation to vision

  • the retina contains photoreceptor cells that detect light and transmit information to the brain

• describe some familiar examples of scattering and dispersion

  • scattering- the random scattering of light in all directions

  • dispersion- the separation of white light into it component colours (e.g.) a rainbow