Understanding Pin-Hole Cameras

Colours

• The primary colours are red, green, and blue.
• Red + Green = Yellow
• Green + Blue = Cyan
• Blue + Red = Magenta

Sound

• Sound is created by vibrations, which travel through the air as waves.
• Sound travels faster in solids because the particles are closer together, making vibration transmission easier.
• Higher frequency means the sound waves are more squashed together, while higher amplitude means the sound waves have a larger height.
• Lower frequency means the sound waves spread apart, while lower amplitude means the sound waves have a smaller height.
• The greater the amplitude of sound, the louder it is.
• The smaller the amplitude of sound, the quieter it is.
• The smaller the frequency of a sound, the lower its pitch.
• Human audible frequency range: 20 Hz to 20,000 Hz.

Noise Cancelling Headphones

• Noise cancelling headphones work by generating an 'out of step' wave that interferes destructively with external noise, cancelling it out.

Pin-hole Cameras

• Light travels in a straight line, so the image is inverted in a pin-hole camera.
• The smaller the pinhole, the sharper the image.
• Increasing the distance between the screen and object results in a blurrier image.
• Reducing the distance between the screen and object results in a sharper image.

Reflection

• Reflection occurs when light travelling through one material bounces off a different material.
• The Law of Reflection states that the angle of incidence equals the angle of reflection.
• Smooth surfaces produce parallel rays, allowing us to see the image, while rough surfaces scatter rays, producing diffuse reflection.

Plane Mirrors

• Images on plane mirrors are laterally inverted and cannot touch the screen, making them virtual.
• The image 'behind' the mirror is the same size and distance from it.

Refraction

• Light changes speed as it passes from one medium to another.
• The frequency of light does not change as it refracts.
• The refractive index of a material measures the change in light speed as it passes from a vacuum into the material.

Light Dispersion

• White light disperses into its constituent colours when passing through a prism.
• Different colour wavelengths are refracted by different amounts.
• Red is refracted the least, and violet is refracted the most.
• ROY G.BIV is a mnemonic for remembering the colours of the visible spectrum.

Colour Filters

• Coloured filters transmit some colours and absorb all others.
• Objects appear white if they reflect all colours, and black if they absorb all colours.
• Coloured objects reflect some colours and absorb others.

Ear Anatomy

• The pinna collects sound vibrations, which are funnelled through the ear canal to the eardrum.
• The eardrum vibrates, and these vibrations are passed on to the ossicles, and then to the cochlea.
• The cochlea converts the vibrations into electrical signals, which are transmitted to the brain through the nerve.
• The semicircular canals help with balance.

How We See

• The retina is the part of the eye where images are formed.
• The convex lens refracts light, causing the light rays to converge and focus.
• The lens can change shape to focus light from objects at different distances.

Digital Image Sensors

• Digital image sensors absorb the energy carried by light waves from the image.
• The energy from the light waves causes the sensor to generate an electrical charge.
• The changes in electrical charge are read by a computer and turned into an image.

Mirrors

• Smooth surfaces, like mirrors, reflect light rays at the same angle, producing a clear reflection.
• Rough surfaces, like cardboard, scatter light rays, making it impossible to see a reflection.

Sound Waves

• Electric signals cause sound waves when they reach a speaker, making the cone vibrate.
• Longitudinal waves, like sound waves, vibrate in the same direction as the wave.
• Light waves are transverse waves, vibrating perpendicularly to the wave direction.

Medium

• A medium is a material that transfers energy, like light or sound, from one substance to another.