Y8 Physics (Light and Colour)

How does light travel?

Light travels in straight lines called rays.

What is an opaque object?

An opaque object is an object that light cannot travel through.

What is an example of an opaque object?

An example of an opaque object is a book.

What is a transparent object?

A transparent object is an object that light can travel through.

What is an example of a transparent object?

An example of a transparent object is Glass.

What is a translucent object?

A translucent object is an object that you can only see a glow of light through.

What is an example of a translucent object?

An example of a translucent object is frosted glass.

What is light made up of?

Light is made up of photons

How does light behave like?

Light behaves mainly like a wave.

What is a luminous object?

A luminous object is an object that emits light.

What is an example of a luminous object?

An example of a luminous object is a star.

What is a non-luminous object?

A non-luminous object is a object that doesn't emit light but reflects it.

What is an example of a non-luminous object?

An example of a non-lumious object is a book.

How do rays of light reach our eyes?

Light is emitted by luminous objects (such as a lamp) and it is reflected off a non-luminous object (such as a book) and is absorbed by our eyes.

What are waves?

Waves are transfers of energy.

What do waves involve?

Waves involve oscillations (vibrations)

What are the two types of waves?

The two types of waves are Longitudinal and Transverse waves.

What is a transverse wave?

A tranverse wave is one where its oscillations are perpendicular to the direction of energy transfer.

What type of wave is light?

Light is a transverse wave.

What is a longitudinal wave?

A longitudinal wave is one where its oscillations are parallel to the direction of energy transfer.

What type of wave is sound?

Sound is a longitudinal wave.

What are the properties of waves?

The properties of waves include the peak/crest, amplitude, wavelength and trough.

What is the peak/crest of a wave?

The peak/crest of a wave is the highest point of a wave.

What is the amplitude of a wave?

The amplitude of a wave is the maximum displacement from the equillibrium position on a wave.

What is amplitude measured in?

Amplitude is measured in metres (m).

How does amplitude determine a wave's brightness?

Amplitude determines a wave's brightness as a large amplitude results in a bright light whereas a small amplitude results in a dim light.

What is the wavelength of a wave?

The wavelength is the length of one complete wave.

What is wavelength measured in?

Wavelength is measured in metres (m).

What is the symbol for wavelength?

The symbol for wavelength is λ.

What is the period of a wave?

The period of a wave is the time taken for one complete oscillation to take place.

What is period measured in?

Period is measured in seconds (s).

What is the trough of a wave?

A trough is the lowest point of a wave.

What is the Frequency (f) of a wave?

The frequency (f) of a wave is the number of oscillations in on second.

What is frequency measured in?

Frequency is measured in Hertz (Hz).

What does a Hz equal?

A Hz equals one oscillation in a second.

What does kHz equal in Hz?

kHz equals one thousand Hz in a second.

What does MHz equal in Hz?

MHz equals one million Hz in a second

What is the wave equation?

The wave equation is: wave speed (v) = frequency (f) x wavelength (λ).

What do light waves travel through?

Light waves travel through a vacuum and don't need a medium.

What do sound waves travel through?

Sound waves can't travel through a vacuum and needs a medium.

What is the speed of light?

The speed of light = 3 x 10^8 m/s (300000000m/s)

What is the speed of sound?

The speed of sound = 3.4 x 10^2 m/s (340m/s)

What is Reflection?

Reflection is when light bounces off a surface and changes direction

surface and changes direction.

What is the law of reflection?

The law of reflection is that Angle of incidence always = Angle of Reflection.

What is specular reflection?

Specular reflection is when light reflects on smooth and shiny surfaces at the same angle as it hit the surface.

What is diffuse reflection?

Diffuse reflection is when light hits rough surfaces and reflects in lots of different directions.

What is a concave mirror?

A concave mirror is one that curves inwards, like the inside of a bowl.

What is a convex mirror ?

A convex mirror is one that curves outwards, like the top of a dome.

Does the law of reflection still apply for curved mirrors?

Yes, the Law of Reflection still applies for curved mirrors.

What is refraction?

Refraction is the bending of light when it travels from one medium to another.

How does refraction occur?

Refraction occurs when light travels from one medium into at an angle and the difference in speed causes a change in direction of the light.

Why does a pencil appear to bend when placed in a beaker of water?

A pencil appears to bend when placed in a beaker of water because light is refracted as it crosses the air-water interface.

How can you predict whether light will bend towards or away from the normal?

Light bends towards the normal when it enters a denser medium, and away from it when it enters a less dense medium.

What is the critical angle?

The critical angle is the angle of incidence where the angle of refraction equals 90°, and anything above this results in total internal reflection.

What is total internal reflection?

Total internal reflection refers to the complete reflection of a light ray at an interface with a less dense medium when the incidence angle exceeds the critical angle.

What is dispersion of light?

Dispersion of light occurs when white light is separated into its constituent colors through a medium like a prism.

Why does white light split up into different colours when it goes through a prism?

White light splits up into different colours when it goes through a prism because each colour is refracted by a different amount of white light.

What is white light?

White light is light that has all the colours of the visible spectrum in it.

What is the visible spectrum?

The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye.

What are the colous of the visible spectrum?

The colous of the visible spectrum include red, orange, yellow, green, blue, indigo and violet.

What is the acronym used for the colours of the visible spectrum?

ROY G BIV is the acronym used for the colours of the visible spectrum.

What colour in the visible spectrum refracts the least?

Red is the colour in the visible spectrum that refracts the least

What colour in the visible spectrum refracts the most?

Violet is the colour in the visible spectrum that refracts the most.

What are the additive/primary colours of light?

Green, Red, and Blue are the additive/primary colours of light.

What happens when you mix two of the additive colours?

You make one of the subtractive colours when you mix two of the additive colours.

What happens when you mix green and red?

You get yellow when you mix green and red.

What happens when you mix blue and red?

You get magenta when you mix blue and red.

What happens when you mix green and blue?

You get cyan when you mix green and blue.

What happens when all of the additive colours are combined?

The colours result in white when all of the additive colours are combined.

What are the subtractive/primary colours of paint?

Yellow, Magenta, and Cyan are the subtractive/primary colours of paint.

What happens when you mix two of the subtractive colours?

You make one of the additive colours when you mix two of the subtractive colours.

What happens when you mix magenta and yellow?

You get red when you mix magenta and yellow.

What happens when you mix yellow and cyan?

You get green when you mix yellow and cyan.

What happens when you mix magenta and cyan?

You get blue when you mix magenta and cyan.

What happens when all of the subtractive colours are combined?

The colours result in black when all of the subtractive colours are combined.

What is black?

Black is the absence of light.

Why do objects appear in the colour they do?

Objects appear in the color they do because they absorb certain wavelengths of light and reflect others.

How does a red shirt look red?

A red shirt appears red because the dye molecules in the fabric absorb most wavelengths of white light, but the red wavelengths of white light are reflected back towards the eye, allowing us to perceive the shirt as red.

What happens when a red shirt is not lit by red light but is exposed to blue light?

A red shirt will appear black when exposed to a blue light, as it only reflects red light and absorbs all other colors, resulting in no red light reflection.

What are the two types of photoreceptors in the retina of our eyes?

The two types of photoreceptors in the retina of our eyes include rods and cones.

What do cones detect?

Cones detect colour.

What do rods let us see?

Rods only let us see thing in black, white and grey.

When do cones work?

Cones only work when the light is bright enough.

Why can we not see colours at night?

At night, when the light is dim, cones do not work, so we can't see colours.

Why do light wave have different colours?

Light waves have different colours because each colour has a different wavelength. Shorter wavelengths make violet and blue, which carry more energy while longer ones make red and carry less energy.