AQA GCSE Physics P14 Light Kerboodle Answers

P14. 1 Reflection of light AQA GCSE Physics P14 Light Kerboodle Answers: Page No. 203

1 a i The law of reflection states that the angle of incidence = the angle of reflection. Soif the angle of reflection is 20 then the angle of incidence = 20⁰.

ii The angle between the incident ray and the reflected ray is 40⁰, because the angle between incident ray and reflected ray = 20⁰+20⁰ = 40⁰.

b If the mirror is turned and the angle of incidence is increased to 21 then the angle between incident ray and reflected ray will become 42⁰.

The path of the two rays shown from O after they have been reflected from the mirror is shown in the figure below–

b I

ii Since R= infinity for a plane mirror,

By using mirror formula
hence, 1/v+1/u = 2/R

So  1/v=-1/u
v = -u.

bi The angle between the final reflected ray and the incident ray is 180⁰.

ii

Normal N1 perpendicular to normal N2

=180⁰.

Rays after reflection from two mutually perpendicular mirrors becomes anti parallel.

a The specular and diffuse reflection can be distinguished as-

Reflection from a smooth surface is called specular reflection because parallel light rays are reflected in a single direction.Parallel light rays reflected from a rough surface are scattered in different directions. If you polish a rough surface like a dusty table top to make it smooth, you might see a reflection in the surface. Reflection from a rough surface is called diffuse reflection because the tight is scattered in different directions.

b The image formed by a plane mirror is virtual, upright (the same way up as the object), and laterally inverted (back to front but not upside down). A virtual image is formed at a place where light rays appear to come from after they have been reflected (or refracted). It can’t be projected onto a screen like the movie images you see at a cinema. An image that can be seen on a screen is described as a real Image because it is formed by focusing light rays onto the screen. The aforesaid are the differences between the real and virtual image.

P14.2 Refraction of light AQA GCSE Physics P14 Light Kerboodle Answers : Page No. 205

a There is a Decrease in speed of ligjt waves when they cross the boundary.

b If the angle of incidence is 0 then the angle of refraction is Less than zero.

c If angle of incidence is non-zero then the angle of refraction is smaller than angle of incidence.

a

b The swimming pool apoears to be shallower than it is really when viewed from abovebecause the rays of light reaching you from the object at the bottom of the water do not come straight to you, as they would if there was no water between you and the object. The light travels straight as long as it is in the water, but if it emerges obliquely from the water into the air it is bent downward toward the surface. This bending is known as refraction, and it occurs whenever light passes from one transparent medium into another of different density – as, for example, from water to air, or from air to glass. The eyes do not take refraction into account, but judge the position of the object as if the light came in a straight line.

4

When white light passes through a transparent medium (like air) into another (like glass), its components are deflected the first time according to their colour, and once again when they reemerge (back into air, for example). This creates a spread of coloured light rays from red to violet, like the colours of the rainbow. So we observe these seven colors on the screen when a white light is placed in the path of a narrow beam of white light.

This ordered separation of coloured rays is known as the “spectrum”. The spectrum of white light consists of six basic colours arranged in a specific order: red, orange, yellow, green, blue and violet.

P14.3 Light and colour AQA GCSE Physics P14 Light Kerboodle Answers : Page No. 207

1 Its front cover appears black in appearance of red light anda white title  has no pigments, so it reflects light of any wavelength, either partially or totally. The surface looks white in daylight because daylight is white light and the reflected light contain red color in presence of red light.

2 The dress appears to be black due to the mixing of color in a scene where there is a blue light.

3 When a white light is directed through the first filter then due to its red colour it absorbs white light it emit only red light and red light on passing through blue filter emit black light.

P14.4 Lenses AQA GCSE Physics P14 Light Kerboodle Answers : Page No. 209

1 a The differences between a real image and a virtual image can be understood as follows-

1. a) A real imageis always inverted whereas a virtual imageis always erect.
2. b) A real imageis formed when the rays of light after reflection or refraction actually meet at some point whereas a virtual imageis formed when the rays of light after reflection or refraction appear to meet at a point.

b

A real image is formed by a convex lens of a diatant object on a screen.

ii With the object nearer to the lens than the principal focus, a magnified image is formed.The image is a virtual image because it is formed where the rays appear to come from. In this situation, the convex lens is used as a magnifying glass.

Iiia The image formed by concave lens is seen to be virtual,erect and highly diminished than the object when the lens in used to form an image of a distant object.

2 a When a postage stamp is inspecred using convex lens as a magnifying glass the image is a virtual image because it is formed where the rays appear to come from.

b i The image formed by convex lens is seen to be real,inverted and diminished.

ii When the screen is moved away from the lens, the object is moved nearer to the lens toward its principal focus.

ci In the magnification of the fiower, the image is a virtual image because it is formed where the rays appear to come from.In this situation, the lens acts as a magnifying glass.

ii

If the flower is close to the lens the light rays enter at a sharper angled. This results in the rays converging away from the lens. As the lens can only bend the light to a certain agree the image needs to be focused in order to form on the film. This is achieved by moving the lens away from the film. Similarly, if the lens is moved away from the flower the rays enter at a wider angle. This results in the rays being refracted at a sharper angle and the image forming closer to the lens. In this case the lens needs to be positioned closer to the film to get a focused image.

3 a The image of the bird in figure 6b is bigger than the object (Figure 6b), the magnification is greater than 1.

b With the object at different distances beyond the principal focus of the lens, adjust the position of the screen until you see a clear image of the object on it. This is a real image because it can be formed on a screen. When the lens is moved further away from the bird and the card is moved to obtain a new clear image, the image is formed at the principal focus of the lens. This is because the rays from any point on the object are almost parallel to each other when they reach the lens. If the object is moved nearer to the lens towards its principal focus, the screen must be moved further from the lens for you to see a clear image. The nearer the object is to the lens, the larger the image with the object nearer to the lens than the principal focus, a magnified image is formed.The image is a virtual image because it is formed where the rays appear to come from. In this situation, the lens acts as a magnifying glass.

4 The following experiment can be used to find the magnification prodiced by the convex lens depends on the distance. With the object at different distances beyond the principal focus of the lens, adjust .The position of the screen until you see a clear image of the object on it. This is a real image because it can be formed on a screen.

• When the object is a long distance away, the image is formed at the principal focus of the lens. This is because the rays from any point on the object are almost parallel to each other when they reach the lens.
• If the object is moved nearer to the lens towards its principal focus, the screen must be moved further from the lens for you to see a clear image. The nearer the object is to the lens, the larger the image.

With the object nearer to the lens than the principal focus, a magnified image is formed.The image is a virtual image because it is formed where the rays appear to come from. In this situation, the lens acts as a magnifying glass.

P14.5 Using lenses AQA GCSE Physics P14 Light Kerboodle Answers : Page No. 211

a

2 a The image is real.

ii magnified or diminished 

The image formed is Diminished.

iii upright or inverted. 

The image is Inverted.

A convex lens is used as a magnifying glass when the object is placed between the lens and its principal focus the image is formed on the same side of the lens as the object. The image is virtual, upright, and larger than the object. The image can be seen only by looking at it through the lens. This is how a magnifying glass works.

b The image formed is virtual.

ii magnified or diminished 

The image formed is magnified.

iii upright or inverted. 

The image formed is Upright.

c Convex lens is not used as a magnifying glass because the image formed by a concave lens is always virtual, upright, and smaller than the object.

3 a Draw two arrows on the axis of your scale diagram, which are 8 cm apart, one twice as big as the other. Now draw a line from the top of the bigger arrow through the top of the smaller arrow. Where this meets the axis is the position of the lens (this should be 8cm on the other side?) so now complete the ray diagram by drawing a line parallel to the axis from the top of the small arrow to the lens, then to the focal point on the other side. Then extrapolate this back to the top of the large arrow.

b If the object is moved gradually towards the focal point of the lens towards its principal focus, the screen must be moved further from the lens for you to see a clear image. The nearer the object is to the lens, the larger the image and the image is real.

4 i

ii The image formed is Real , inverted and the magnification is 1 i.e image is of same size as the object.

b An application for the use of lens is-

In a camera, a convex lens is used to produce a real image of an object on a film (or on an array of pixels for a digital camera). The position of the lens is adjusted to focus the image on the film.

• For a distant object, the distance from the lens to the film must be equal to the focal length of the lens.
• The nearer an object is to the lens, the bigger is the distance from the lens to the film.

Summary questions: Page No. 212

1

i Angle x is angle of incidence and Angle y is angle of reflection,

x = y

ii

two correctly reflected rays and normals shown

each reflected ray at same angle to normal as incident ray

image located by tracing two reflected rays back and labelled at correct position

jji The distance from the image to the mirror is same as the distance of the object from the mirror.

B An experiment to test the law of reflection using the ray box and the plane mirror can be described as follows-

draw straight line XY on white paper and use protractor to draw ‘normal’ perpendicular to XY,

place mirror exactly on XY and direct light at point P where normal intersects XY using ray box,

adjust direction of light ray so angle of incidence ≈ 10°, mark direction of incident and reflected rays,

remove mirror and use protractor to measure angles of incidence and reflection,

repeat for different angles of incidence,

record all results in table, results should show angle of incidence = angle of reflection

2 a

i both refractions correct

rays before and after passing through block parallel to each other

ii

The ray emerging from the block is exactly parallel to the incident ray because-

change in direction at second refraction exactly equal and opposite to change at first refraction,

emerging light parallel to incident light because opposite sides of block parallel

b first refraction towards normal,

2nd refraction away from normal

3 a The difference between specular and diffuse reflection is as follows-

1. specular reflection parallel light rays are reflected in a single direction
2. diffuse reflection the light is scattered in different directions

bi Translunce materialare the materials that allow light to pass through but scatters it, i.e. images are not seen.

ii Translucence is caused because the material has many internal boundaries

that repeatedly change direction of light rays

4

ai The type of lens that is shown in this diagram is converging

ii 2 construction rays correct

image correct

b The image is real, inverted and smaller than the object

An application of the lens used in this way is camera.

5 a at least 2 construction rays correct

image correct in correct position

b The image formed is real.

c The magnification produced by the lens is 1.7

6 a at least 2 construction rays correct and image correct

b Determine whether the image is:

i real or virtual

The image is virtual

ii The image is upright

7 a at least 2 construction rays correct

and image correct

b Determine whether the image in a is:

i The image is virtual

ii The image is upright

Practice questions: Page No. 213

01.1 A red and blue rugby shirt hanging on the line appeears red and blue because the red part absorbs all colours except red and the blue part absorbs all colours except blue and therefore blue and red are reflected

01.2 Skirt and Shirt appear black and white because black absorbs all colours in the spectrum and white reflects all colours in the spectrum

01.3 transparent – clear glass

translucent – frosted glass

opaque – black glass

02.1

correct labels

02.2

When the light is reflected from a smooth surface it is called specular reflection.

When the light is reflectes from a rough surface it is called diffuse reflection.

03.1

The range of the angles of incidence used in the investigation is 5–90 degrees (accept 0–90 degrees)

03.2 One way of improving the investigation is to calculate the mean of the results and draw one line

03.3 The name of possible error is systematic error

03.4 The percentage of light reflected changes with the angle of incidence as the angle of incidence increases the % reflection increases but not at a constant rate

04Figure3 shows a lens, the position of an object, and the position of the image.

04.1 The type of the lens shown is convex lens

04.2 The name of the points F shown on each side of the lens is focal point

04.3

The image shown is inverted and real.

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References:

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