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Science > Light > Flashcards

Light Flashcards

1
Q

Light

A

A beam of energy called a ray. Light always moves in straight lines and cannot bend around objects. There are two types of light: natural and artificial. E.g. The Sun is natural, a light bulb is artificial.

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2
Q

Ray

A

A beam of energy.

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3
Q

Luminous

A

Everything that creates its own light. (Both natural and artificial sources.)

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4
Q

Non-Luminous

A

Objects that create light, but not by themselves. E.g. The Moon.

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5
Q

Speed of light

A

300,000 km/s is the speed of light. This is the fastest speed that anything can go at. Light only slows down when it encounters things like air or water. And even then, only by a small amount. The amount it slows down depends on the density of the object.

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6
Q

Radio Waves

A

Low energy electromagnetic waves with a much lower frequency and longer wavelength than visible light.

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7
Q

Infra-Red Radiation

A

Invisible radiation emitted by all warm objects. You feel infra-red radiation as heat.

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8
Q

Visible Light

A

Very small part of the electromagnetic spectrum to which our eyes are sensitive.

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9
Q

Ultraviolet Radiation (UV)

A

Invisible radiation similar to light but with a slightly higher frequency and more energy.

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10
Q

X-Rays

A

High-energy electromagnetic waves that can be transmitted through solids and provide information about their structure.

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11
Q

Gamma Rays

A

High-energy electromagnetic radiation produced during nuclear reactions. They have no mass and travel at the speed of light.

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12
Q

Electromagnetic Waves

A

Electromagnetic energy that is transmitted by moving electric and magnetic fields. There are many different types of electromagnetic energy, e.g. light, microwaves, radio waves.

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13
Q

Reflection

A

Something bouncing off the surface of another. substance.

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14
Q

Scattering

A

Describes light sent in many directions by small particles within a substance.

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15
Q

Transparent

A

Describes a substance that allows most light to pass through it. Objects can be seen clearly through transparent substances.

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16
Q

Translucent

A

Allowing light to come through imperfectly, as in frosted glass.

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17
Q

Opaque

A

Describes a substance that does not allow any light to pass through it.

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18
Q

Convex

A

Curved outwards.

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19
Q

Concave

A

Curved inwards.

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20
Q

Lateral Inversion

A

Something that is reversed sideways. This means that left and right are flipped over.

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21
Q

Refraction

A

Change in the speed of light as it passes from one substance into another. It usually involves a change in direction.

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22
Q

Model

A

A diagram helping one to understand a particular concept or theory. E.g. Particle model of matter helps us to understand the states of matter.

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23
Q

Photons

A

Particles such as a quantum of light or electromagnetism.

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24
Q

Normal

A

A line that is drawn along the point where the incident ray hits the mirror and reflects away. It is usually used to help draw a reflection diagram. The normal is always at a right angle (90 ∘ ) to the surface of the mirror.

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25
Q

Focal Point

A

The point at which rays or waves meet after reflection or refraction.

26
Q

Transverse Waves

A

When light moves through a medium the energy vibrates at right angles to the direction that it is travelling in.

27
Q

Frequency

A

The number of crests that pass a certain point in one second. Visible light has an extremely high frequency and a very short wavelength.

28
Q

Wavelength

A

The distance between two peaks/troughs. The longer the wavelength, the shorter frequency.

29
Q

Crest/Peak

A

The top of a wave.

30
Q

Trough

A

The bottom/base of a wave.

31
Q

Equilibrium

A

The line that passes through the centre of a wave.

32
Q

Amplitude

A

The distance from the equilibrium to the crest or trough. (Both are the same distance).

33
Q

Electromagnetic Spectrum

A

Complete range of wavelengths of energy radiated as electric and magnetic fields. (We can only see a small part of it).

34
Q

Energy

A

Power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines.

35
Q

Shadow

A

A shadow is produced when light can’t pass through an object.

36
Q

Ray Diagram

A

A diagram that traces the path light takes in order for a person to be able to see an object. Ray diagrams have solid straight lines that represent one or several rays of light. Each line has an arrow on it to show which direction the ray is travelling in.

37
Q

Drawing Ray Diagrams

A

We always draw and label the source of light, the object that the light is hitting, the ground and a single eye to represent the end of the light’s path (as we experience it). Then, we draw the ray of light hitting the object, and then bouncing off to reach the eye. Finally, we draw a direct ray that goes from the source to the eye and label that. (We need to remember the directional arrows on each ray too).

38
Q

Extended Light Sources

A

Light sources that are very large and very far away, like the Sun, or light sources that shine their light over a wide area, like a light bulb or candle. Shadows made from extended sources of light can have both of the two possible shadow parts; the penumbra and Umbra.

39
Q

Umbra

A

A totally dark middle part of a shadow.

40
Q

Penumbra

A

A faint part around the Umbra.

41
Q

Point Source of Light

A

A very slim area that light rays are sent out from. These usually look like bright lines, or laser beams because they are so narrow. When an object blocks a point source of light’s path, it will create a shadow that only has an umbra. (No penumbra). The shadow created will also have the same exact shape as that object.

42
Q

Electromagnetic Radiation

A

A travelling energy that acts like a wave, but, it is not quite a wave. For example, EMR travels through the vacuum of space. Most waves need a medium to travel in - but not EMR. Electromagnetic radiation exists on a spectrum of different types of wave. Light exists in the middle of this spectrum and is defined as the wavelengths of electromagnetic radiation that we can see. Other types of EMR include infrared, microwaves, radio waves, ultraviolet, x-rays and gamma waves.

43
Q

Velocity

A

The speed of something in a given direction.

44
Q

Image

A

A reflection of something that is real. Not a picture.

45
Q

Plane

A

An object that is completely level or flat. Like a plane mirror.

46
Q

Incident Ray

A

A light ray that travels towards a mirror. In diagrams, it is represented by an arrow that points towards the mirror.

47
Q

Reflection Ray

A

A ray that has been reflected from a mirror. It is represented by an arrow that points away from the mirror.

48
Q

Angle of Incidence

A

The angle between the incident ray and the normal.

49
Q

Angle of Reflection

A

The angle between the ray of reflection and the normal.

50
Q

The Law of Reflection

A

The law states that the angle of reflection is equal to the angle of incidence. This means that a light ray reflects off a mirror at the same angle that it hits the mirror at.

51
Q

Retina

A

At the back of the eye. It detects light using cells called photoreceptors and it sends signals to the brain.

52
Q

Iris

A

Controls the size of the pupil. The coloured part of the eye.

53
Q

Pupil

A

Allows light into the eye. It is the black circle in the centre of each eye.

54
Q

Lens

A

Focuses light onto the retina.

55
Q

Optic Nerve

A

Receives signals from the retina and sends them to the brain.

56
Q

Sclera

A

Protects the eye and helps it maintain its shape.

57
Q

Choroid

A

Contains blood vessels, which bring nutrients to the eye.

58
Q

Cornea

A

Protects the front of the eye.

59
Q

Vitreous Humour

A

Helps the eye maintain its shape.

60
Q

Aqueous Humour

A

Brings nutrients to the cornea and lens, which lack blood vessels.

Science (6 decks)

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