Look at the diagram of a glass block surrounded by air. The incident ray is shown. Add the label 'Z ' to the angle of refraction between the normal at Y and the refracted ray.

Light passes in straight line motion until it enters in to different medium. Here the light ray is passing from air to glass. Light ray incidents on point 'X'. The line drawn perpendicular to the surface at the point of incidence is called normal. Glass is a denser medium than air. Light enters from rarer medium to denser medium it bends towards the normal as shown in the diagram. Such that angle of refraction is less than angle of incidence. At point 'Y' the light ray emerges out of the glass slab. Such that angle of incidence and angle of emergence 'Z' are equal i.e. emergent ray is parallel to incident ray.

Look at the diagram of a glass block surrounded by air. The incident ray is shown. State the connection between the original angle of incidence at point X and the final angle of refraction Z at point Y.

Light passes in straight line motion until it enters in to different medium. Here the light ray is passing from air to glass. Light ray incidents on point 'X'. The line drawn perpendicular to the surface at the point of incidence is called normal. Glass is a denser medium than air. Light enters from rarer medium to denser medium it bends towards the normal as shown in the diagram. Such that angle of refraction is less than angle of incidence. At point 'Y' the light ray emerges out of the glass slab. Such that angle of incidence and angle of emergence 'Z' are equal i.e. emergent ray is parallel to incident ray.

Priya designed an experiment to investigate what light does when it falls on different surfaces. She used a special red lamp to shine a light on different surfaces. Priya wrote down these results in a table. Surface Reflected light seen Any other observations Metal painted matte black None (black) After a few minutes, the metal felt warm to the touch. Polished metal (shiny silver) Red light After a few minutes, there was no change in temperature of the metal. Metal polished with a green plastic layer on top None (black) After a few minutes the metal temperature did not appear to change.

The process of sending back light rays which fall on the surface of an object is called the reflection of light. In the first case, Priya shines a metal painted matte which is black with a red lamp. Objects appear black when they do not reflect any light at all. We say that a black object absorbs all the light that shines on it. The effect is called absorption. Here, the red light is absorbed by the black matte, and we cannot see any reflected light. We know that black coloured materials absorb and radiate heat at the fastest rate. Here, the absorbed light energy is converted into heat energy and after a few minutes, the metal felt warm to the touch. In the second case, when red light falls on polished metal, the reflected light will also be red as a polished metal will reflect the same colour of light that falls on it. Here, all the red light that falls on the polished metal surface is reflected and therefore no change in temperature takes place. In the third case, red light falls on a metal that is polished with a green plastic layer on top. Here, it absorbs the red colour of light and no reflection of light happens, as a green colour surface cannot reflect red light. Hence, the reflected light will appear black. Since the green colour does not have good absorbing power as black, it will not radiate heat as black colour does. So after a few minutes, the metal temperature did not appear to change.

EASY

Lower Secondary Stage 8

IMPORTANT

Earn 100

Look at the diagram of a glass block surrounded by air. The incident ray is shown.

Add the label 'Y' where your first refracted glass ray leaves the glass block.

Important Questions on Light

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 3>Q 6

Look at the diagram of a glass block surrounded by air. The incident ray is shown.

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Think about what happens at the point you have labelled Y. Draw a normal at Y and the path of the refracted ray through the air to the right of the glass block.

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 3>Q 6

Look at the diagram of a glass block surrounded by air. The incident ray is shown.

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Add the label 'Z ' to the angle of refraction between the normal at Y and the refracted ray.

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 3>Q 6

Look at the diagram of a glass block surrounded by air. The incident ray is shown.

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State the connection between the original angle of incidence at point X and the final angle of refraction Z at point Y.

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 4>Q 3

The diagram shows three large coloured lamps arranged one above the other. They shine through a thick glass block onto a screen.
The orange light ray shown hits the block at a right-angle. Complete the ray diagram for the orange light. Label the point on the screen where the ray arrives with the letter 'X'.

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EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 4>Q 3

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Add rays for the red and green lamps to show rays that also arrive at point 'X'.

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 4>Q 5

Look at the diagram showing different surfaces. Predict what will be observed when light falls on each surface. Complete the table with your answers.

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MEDIUM

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Exercise 4>Q 6

Priya designed an experiment to investigate what light does when it falls on different surfaces. She used a special red lamp to shine a light on different surfaces. Priya wrote down these results in a table.

Surface	Reflected light seen	Any other observations
Metal painted matte black	None (black)	After a few minutes, the metal felt warm to the touch.
Polished metal (shiny silver)	Red light	After a few minutes, there was no change in temperature of the metal.
Metal polished with a green plastic layer on top	None (black)	After a few minutes the metal temperature did not appear to change.

EASY

Lower Secondary Stage 8

IMPORTANT

Cambridge Lower Secondary Science Stage 8 : Workbook>Chapter 7 - Light>Test-style questions>Q 1

The diagram shows an experiment investigating light.
Name the effect an experiment shows.

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Look at the diagram of a glass block surrounded by air. The incident ray is shown. Add the label 'Y' where your first refracted glass ray leaves the glass block.

Important Questions on Light

Learn and Prepare for any exam you want !

Look at the diagram of a glass block surrounded by air. The incident ray is shown.

Add the label 'Y' where your first refracted glass ray leaves the glass block.