| Term | Definition |
|---|---|
What do waves transfer from one place to another? | Energy |
Do waves transfer matter as they travel? | No, waves transfer energy without transferring matter |
How many types of wave are there? | Two — transverse and longitudinal |
Name the two types of wave | Transverse and longitudinal |
In a transverse wave, which way do particles move relative to the wave's direction of travel? | At right angles (perpendicular) to the direction of energy travel |
Name two examples of transverse waves | Water waves and light (electromagnetic radiation) |
Is light a transverse or longitudinal wave? | Transverse |
Are water waves transverse or longitudinal? | Transverse |
In a longitudinal wave, which way do particles move relative to the wave's direction of travel? | Parallel to the direction of energy travel |
Give an example of a longitudinal wave | Sound |
Is sound a transverse or longitudinal wave? | Longitudinal |
What is the definition of period (T)? | The time taken for one wave to pass a point |
What is the definition of frequency (f)? | The number of waves each second |
What is the definition of amplitude? | The distance from the mid-line to a wave crest or trough |
What is the definition of wavelength (λ)? | The distance between a point on a wave and the identical point on the next wave |
What is the definition of wave speed (v)? | The distance the wave travels each second |
Which symbol represents period? | T |
Which symbol represents frequency? | f |
Which symbol represents wavelength? | λ |
Which symbol represents wave speed? | v |
What is the formula for frequency in terms of number of waves and time? | f = N/t |
In f = N/t, what does N stand for? | The number of waves produced or passing a point |
In f = N/t, what does t stand for? | The time taken for the waves to be produced or to pass a point |
What is the formula linking period and frequency? | T = 1/f |
If you know the frequency, how do you calculate the period? | Take the reciprocal: T = 1/f |
What is the formula for wave speed using frequency and wavelength? | v = fλ |
What is the formula for wave speed using distance and time? | v = d/t |
In v = fλ, what unit is used for wave speed? | Metres per second (m s⁻¹) |
In v = fλ, what unit is used for wavelength? | Metres (m) |
In v = fλ, what unit is used for frequency? | Hertz (Hz) |
In v = d/t, what unit is used for distance? | Metres (m) |
In v = d/t, what unit is used for time? | Seconds (s) |
What term describes waves bending when they meet an obstacle or pass through a gap? | Diffraction |
What piece of apparatus is used to study the behaviour of water waves? | A ripple tank |
What produces plane (straight) waves in a ripple tank? | A vibrating bar |
What happens to plane waves when they meet a barrier with a small gap? | They appear on the other side as circular waves centred on the gap |
Which diffracts more around a hill: long wavelength or short wavelength waves? | Long wavelength waves |
Will radio waves diffract around a large hill or building? | Yes |
Will short-wave, higher-frequency TV broadcasts diffract around a hill as easily as radio waves? | No, they are more likely to be blocked by the hill |
Why do long radio broadcasts bend around hills more easily than TV broadcasts? | Because they have a longer wavelength, and longer wavelengths diffract more |
What speed do all electromagnetic waves travel at in a vacuum? | 3 × 10⁸ m s⁻¹ (the speed of light) |
What type of wave is every band of the electromagnetic spectrum? | Transverse |
Can electromagnetic radiation travel through a vacuum? | Yes |
What determines how much energy an EM wave carries? | Its frequency — the higher the frequency, the more energy it carries |
Which two EM waves are the most dangerous, and why? | X-rays and gamma radiation, because they have the highest frequency and carry the most energy |
List the seven bands of the EM spectrum in order of increasing frequency | Radio/TV waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma radiation |
Which EM wave has the longest wavelength? | Radio and TV waves |
How are radio and TV waves detected? | By an antenna or aerial tuned to the wave's particular frequency |
What can radio and TV waves carry, and how is it used? | Information, which the receiver decodes to produce sound or visual images |
Name two common uses of microwaves | Telecommunication/mobile phones and microwave ovens |
How do microwave ovens cook food? | The microwaves cause water molecules in the food to vibrate, generating heat |
What health concern is associated with microwaves? | Excessive use of a mobile phone close to the head, in high doses |
What kind of object emits infrared radiation? | Any object hotter than its surroundings |
How can infrared radiation be detected? | With special cameras or infrared film |
Name a medical use of infrared radiation | Treating muscle injuries, or thermal imaging to help diagnose disease |
Name a household/engineering use of infrared photography | Identifying where houses are losing heat, or where overhead electric cables are overheating due to a fault |
Which part of the eye detects visible light? | The retina |
What determines the colour of visible light we perceive? | Its wavelength or frequency |
Where does ultraviolet light typically come from? | The Sun, or special lamps |
What effect does UV light have on skin (positive/expected)? | It causes skin to tan |
What dangerous effect can UV light have on skin? | Severe skin damage, including skin cancer |
What effect does UV light have on certain materials? | It causes them to fluoresce or glow |
Give an application that relies on UV-induced fluorescence | Showing up security markings, or special dyes used to print genuine bank notes |
What special ability of X-rays is exploited in medicine? | Their ability to pass through the human body |
How are X-ray images typically captured? | On photographic film |
Why does bone appear pale on an X-ray image? | Dense tissue like bone blocks X-rays more than soft tissue does |
Why does soft tissue appear darker on an X-ray image? | Because it blocks fewer X-rays than dense tissue like bone |
Why does a metal object appear completely white on an X-ray image? | Because it completely blocks the X-rays |
Which EM radiation is potentially the most dangerous of all? | Gamma radiation |
How is gamma radiation used to investigate the body, despite being dangerous? | A gamma-emitting liquid is injected into the patient |
What can gamma radiation reveal inside the body once injected? | Blood flow, tumours, or particular organs such as the thyroid gland |
What device captures an image using gamma radiation from inside a patient? | A gamma camera |
Give an example of an organ imaged using a gamma camera | The thyroid gland |
How can gamma radiation be used to destroy tumours? | A beam of radiation is directed at the tumour from several different directions |
Why is a gamma beam directed from several different directions when treating a tumour? | So the tumour receives a full dose of radiation while surrounding healthy tissue receives a lesser dose |
What is refraction? | The change in speed, wavelength and (usually) direction of a wave as it passes from one medium into another |
What is the 'normal' in a refraction diagram? | A line at 90° to the surface at the point where the ray meets it |
When a ray of light travels from air into glass, what happens to its speed? | It slows down |
When a ray of light travels from air into glass, what happens to its wavelength? | It decreases |
When a ray of light travels from air into glass at an angle, what happens to its direction? | It refracts or bends towards the normal |
When a ray of light travels from glass into air, what happens to its speed? | It speeds up |
When a ray of light travels from glass into air, what happens to its wavelength? | It increases |
When a ray of light travels from glass into air at an angle, what happens to its direction? | It refracts or bends away from the normal |
What property of light stays the same during refraction? | Its frequency |
What happens to a ray of light that enters a glass block along the normal? | It does not change direction |
What happens to light passing straight through a parallel-sided glass block (not along the normal)? | It emerges parallel to the incident beam, though offset, due to refraction |
Why does a straw in a glass of water appear bent? | Because of the refraction of light as it passes between water and air |
How can refraction be applied in optics to bend light paths intentionally? | Through lenses, which can be convex or concave |
What natural phenomenon does the refraction of light in a prism cause? | Splitting white light into its component colours |
Which colour of light is refracted least by a prism? | Red |
Which colour of light is refracted most by a prism? | Violet |
What is the approximate wavelength of red light? | 700 nm |
What is the approximate wavelength of violet light? | 400 nm |
What shape of glass block is used to demonstrate total internal reflection? | A semi-circular glass block |
As the angle of incidence increases in a semi-circular block, what happens to the refracted ray? | It bends further away from the normal |
What is the critical angle? | The angle of incidence at which light is refracted at exactly 90° along the glass face |
What happens to light entering a glass block at an angle greater than the critical angle? | All the light is reflected back into the glass — total internal reflection |
What law does light obey during total internal reflection? | The law of reflection — the angle of incidence equals the angle of reflection |
Give a major real-world application of total internal reflection | Optical fibres |
What are optical fibres made of? | Fine glass fibres |
Why does light stay inside an optical fibre as it travels along it? | Because of total internal reflection |
Why are optical fibres widely used in telecommunications? | Because they can carry high volumes of data, e.g. broadband |