Notes - Test Feb 2025

TOPIC LIST

• Explain, with the aid of ray diagrams, reflection, refraction and total internal reflection (TIR), including the law of reflection and critical angle

• Investigate refraction in rectangular glass blocks in terms of the interaction of electromagnetic waves with matter

• Relate the power of a lens to its focal length and shape

• Use ray diagrams to show the similarities and differences in the refraction of light by converging and diverging lenses

• Explain the effects of different types of lens in producing real and virtual images

• Explain the difference between specular and diffuse reflection

• Explain how colour of light is related to a) differential absorption at surfaces b) transmission of light through filters

• Recall that all electromagnetic waves are transverse, that they travel at the same speed in a vacuum

• Explain, with examples, that all electromagnetic waves transfer energy from source to observer

• Recall that our eyes can only detect a limited range of frequencies of electromagnetic radiation

• Recall the main groupings of the continuous electromagnetic spectrum including (in order) radio waves, microwaves, infrared, visible (including the colours of the visible spectrum), ultraviolet, x-rays and gamma rays

• Describe the electromagnetic spectrum as continuous from radio waves to gamma rays and that the radiations within it can be grouped in order of decreasing wavelength and increasing frequency

• Recall that different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength

• Explain the effects of differences in the velocities of electromagnetic waves in different substances

• Describe some uses of electromagnetic radiation

a radio waves: including broadcasting, communications and satellite transmissions

b microwaves: including cooking, communications and satellite transmissions

c infrared: including cooking, thermal imaging, short range communications, optical fibres, television remote controls and security systems

d visible light: including vision, photography and illumination

e ultraviolet: including security marking, fluorescent lamps, detecting forged bank notes and disinfecting water

f x-rays: including observing the internal structure of objects, airport security scanners and medical x-rays

g gamma rays: including sterilising food and medical equipment, and the detection of cancer and its treatment

• Recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits

• Recall that the potential danger associated with an electromagnetic wave increases with increasing frequency

• Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including:

a microwaves: internal heating of body cells

b infrared: skin burns

c ultraviolet: damage to surface cells and eyes, leading to skin cancer and eye conditions

d x-rays and gamma rays: mutation or damage to cells in the body

• Recall that changes in atoms and nuclei can

a generate radiations over a wide frequency range

b be caused by absorption of a range of radiations

• Explain that all bodies emit radiation, that the intensity and wavelength distribution of any emission depends on their temperature

• Explain that for a body to be at a constant temperature it needs to radiate the same average power that it absorbs

• Explain what happens to a body if the average power it radiates is less or more than the average power that it absorbs

• Explain how the temperature of the Earth is affected by factors controlling the balance between incoming radiation and radiation emitted

• Core Practical: Investigate how the nature of a surface affects the amount of thermal energy radiated or absorbed

□ Explain how and why both the weight of any body and the value of g differ between the surface of the Earth and the surface of other bodies in space, including the Moon

□ Recall the difference between mass and weight

□ Recall that our Solar System consists of the Sun (our star), eight planets and their natural satellites (such as our Moon); dwarf planets; asteroids and comets

□ Recall the names and order, in terms of distance from the Sun, of the eight planets

□ Describe how ideas about the structure of the Solar System have changed over time

□ Describe the orbits of moons, planets, comets and artificial satellites

□ Explain for circular orbits how the force of gravity can lead to changing velocity of a planet but unchanged speed

□ Explain how, for a stable orbit, the radius must change if orbital speed changes (qualitative only)

□ Compare the Steady State and Big Bang theories

□ Describe evidence supporting the Big Bang theory, limited to red-shift and the cosmic microwave background (CMB) radiation

□ Recall that as there is more evidence supporting the Big Bang theory than the Steady State theory, it is the currently accepted model for the origin of the Universe

□ Describe that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength (doppler effect)

□ Describe the red-shift in light received from galaxies at different distances away from the Earth

□ Explain why the red-shift of galaxies provides evidence for the Universe expanding

□ Explain how both the Big Bang and Steady State theories of the origin of the Universe both account for red-shift of galaxies

□ Explain how the discovery of the CMB radiation led to the Big Bang theory becoming the currently accepted model

□ Describe the evolution of stars of similar mass to the Sun through the following stages:

a nebula

b star (main sequence)

c red giant

d white dwarf

□ Explain how the balance between thermal expansion and gravity affects the life cycle of stars

□ Describe the evolution of stars with a mass larger than the Sun

□ Describe how methods of observing the Universe have changed over time including why some telescopes are located outside the Earth’s atmosphere