Reflection occurs when a wave hits a boundary between two media and does not pass through it, but instead stays in the original medium.

Refraction occurs when light passes a boundary between two different transparent media and undergoes a change in direction because it changes speed .

State the law of reflection.

The angle of incidence ( i ) is equal to the angle of reflection ( r ).

What is the normal, and how is it used in ray diagrams?

The normal is a line drawn at 90° to the boundary. Angles of incidence and reflection (or refraction) are always measured from the normal, not from the boundary surface.

When light travels from a less dense medium into a more dense medium, it bends ______ the normal.

When light travels from a less dense medium into a more dense medium, it bends towards the normal.

Describe how a light ray bends when it passes from a denser medium into a less dense medium.

It bends away from the normal, for example when light travels from glass into air.

True or False? The frequency of light changes when it refracts.

False. Only the speed and wavelength of light change during refraction; the frequency stays the same.

Define critical angle .

The critical angle (θc) is the angle of incidence at which the angle of refraction is exactly 90°, so the refracted ray travels along the boundary.

Define total internal reflection .

Total internal reflection occurs when the angle of incidence is greater than the critical angle and the incident material is denser than the second material, so all the light reflects back into the first material.

State the two conditions needed for total internal reflection to occur.

The angle of incidence must be greater than the critical angle ( i > θc). The incident material must be denser than the second material.

What happens to a light ray at the boundary when the angle of incidence equals the critical angle?

The light is refracted along the boundary , at an angle of refraction of 90° .

As the angle of incidence increases, the angle of refraction also increases until it reaches ______ .

As the angle of incidence increases, the angle of refraction also increases until it reaches 90° .

True or False? Total internal reflection can occur when light travels from a less dense material into a denser material.

False. Total internal reflection only occurs when light travels from a denser material into a less dense material.

Define specular reflection .

Specular reflection is reflection from a smooth surface in a single direction, where the angle of incidence equals the angle of reflection.

Define diffuse reflection .

Diffuse reflection is reflection from a rough surface that causes the light to be scattered in many directions.

Why can a clear reflection be seen in a mirror but not on a table surface?

A mirror is smooth , so it reflects light in one direction by specular reflection . A table surface is rough at a small scale, so it scatters light in all directions by diffuse reflection .

Why does an object appear red?

The object reflects red light and absorbs all the other frequencies of visible light.

How does a red colour filter affect white light passing through it?

The filter transmits red light and absorbs all the other colours.

When light is absorbed, energy is transferred from the wave into the ______ of a substance.

When light is absorbed, energy is transferred from the wave into the particles of a substance.

True or False? The colour of light transmitted through a filter is the same colour as the filter.

True. A filter transmits only the wavelengths corresponding to its own colour and absorbs the rest.

Define principal focus for a converging lens.

The principal focus is the point where parallel rays of light are brought together after passing through a converging lens.

Define focal length .

The focal length is the distance from the lens to the principal focus.

How does the curvature of a lens affect its focal length?

The more curved the lens, the shorter its focal length.

What is the principal focus of a diverging lens?

The point from which the parallel rays appear to diverge after passing through the lens.

The shorter the focal length, the ______ the power of the lens.

The shorter the focal length, the greater the power of the lens.

True or False? A diverging lens always has a positive focal length.

False. A diverging lens is often given a negative focal length, since it causes light to diverge rather than converge.

A real image is formed when light rays converge and meet each other, and it can be projected onto a screen.

Define virtual image .

A virtual image is formed when light rays appear to meet but do not actually meet, and it cannot be projected onto a screen.

How are real and virtual images shown differently in ray diagrams?

Real images are shown where two solid lines cross. Virtual images are shown where two dashed lines , or one dashed and one solid line, cross.

Where must an object be placed relative to a converging lens's focal length, f , for it to form a real image?

Further from the lens than the focal length, f .

What type of image does a diverging lens always produce?

A diverging lens always produces a virtual , diminished and upright image.

Real images are always ______ , whereas virtual images are always ______ .

Real images are always inverted , whereas virtual images are always upright .

True or False? A converging lens can only produce virtual images.

False. A converging lens can produce either a real image, if the object is beyond f , or a virtual image, if the object is within f .

GCSEPhysicsEdexcelFlashcards5. Light & the Electromagnetic SpectrumOptics

Optics (Edexcel GCSE Physics): Flashcards

Exam code: 1PH0

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Define reflection.

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Cards in this collection (34)

Define reflection.
Reflection occurs when a wave hits a boundary between two media and does not pass through it, but instead stays in the original medium.
Define refraction.
Refraction occurs when light passes a boundary between two different transparent media and undergoes a change in direction because it changes speed.
State the law of reflection.
The angle of incidence (i) is equal to the angle of reflection (r).
What is the normal, and how is it used in ray diagrams?
The normal is a line drawn at 90° to the boundary. Angles of incidence and reflection (or refraction) are always measured from the normal, not from the boundary surface.
When light travels from a less dense medium into a more dense medium, it bends ______ the normal.
When light travels from a less dense medium into a more dense medium, it bends towards the normal.
Describe how a light ray bends when it passes from a denser medium into a less dense medium.
It bends away from the normal, for example when light travels from glass into air.
True or False?
The frequency of light changes when it refracts.
False.
Only the speed and wavelength of light change during refraction; the frequency stays the same.
Define critical angle.
The critical angle (θc) is the angle of incidence at which the angle of refraction is exactly 90°, so the refracted ray travels along the boundary.
Define total internal reflection.
Total internal reflection occurs when the angle of incidence is greater than the critical angle and the incident material is denser than the second material, so all the light reflects back into the first material.
State the two conditions needed for total internal reflection to occur.
The angle of incidence must be greater than the critical angle (i > θc). The incident material must be denser than the second material.
What happens to a light ray at the boundary when the angle of incidence equals the critical angle?
The light is refracted along the boundary, at an angle of refraction of 90°.
As the angle of incidence increases, the angle of refraction also increases until it reaches ______.
As the angle of incidence increases, the angle of refraction also increases until it reaches 90°.
True or False?
Total internal reflection can occur when light travels from a less dense material into a denser material.
False.
Total internal reflection only occurs when light travels from a denser material into a less dense material.
Define specular reflection.
Specular reflection is reflection from a smooth surface in a single direction, where the angle of incidence equals the angle of reflection.
Define diffuse reflection.
Diffuse reflection is reflection from a rough surface that causes the light to be scattered in many directions.
Why can a clear reflection be seen in a mirror but not on a table surface?
A mirror is smooth, so it reflects light in one direction by specular reflection. A table surface is rough at a small scale, so it scatters light in all directions by diffuse reflection.
Why does an object appear red?
The object reflects red light and absorbs all the other frequencies of visible light.
How does a red colour filter affect white light passing through it?
The filter transmits red light and absorbs all the other colours.
When light is absorbed, energy is transferred from the wave into the ______ of a substance.
When light is absorbed, energy is transferred from the wave into the particles of a substance.
True or False?
The colour of light transmitted through a filter is the same colour as the filter.
True.
A filter transmits only the wavelengths corresponding to its own colour and absorbs the rest.
Define principal focus for a converging lens.
The principal focus is the point where parallel rays of light are brought together after passing through a converging lens.
Define focal length.
The focal length is the distance from the lens to the principal focus.
How does the curvature of a lens affect its focal length?
The more curved the lens, the shorter its focal length.
What is the principal focus of a diverging lens?
The point from which the parallel rays appear to diverge after passing through the lens.
State the equation linking power and focal length.
$p o w e r = \frac{1}{f o c a l l e n g t h}$
Power is measured in dioptres.
The shorter the focal length, the ______ the power of the lens.
The shorter the focal length, the greater the power of the lens.
True or False?
A diverging lens always has a positive focal length.
False.
A diverging lens is often given a negative focal length, since it causes light to diverge rather than converge.
Define real image.
A real image is formed when light rays converge and meet each other, and it can be projected onto a screen.
Define virtual image.
A virtual image is formed when light rays appear to meet but do not actually meet, and it cannot be projected onto a screen.
How are real and virtual images shown differently in ray diagrams?
Real images are shown where two solid lines cross. Virtual images are shown where two dashed lines, or one dashed and one solid line, cross.
Where must an object be placed relative to a converging lens's focal length, f, for it to form a real image?
Further from the lens than the focal length, f.
What type of image does a diverging lens always produce?
A diverging lens always produces a virtual, diminished and upright image.
Real images are always ______, whereas virtual images are always ______.
Real images are always inverted, whereas virtual images are always upright.
True or False?
A converging lens can only produce virtual images.
False.
A converging lens can produce either a real image, if the object is beyond f, or a virtual image, if the object is within f.

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