ISLAMIYA ENGLISH SCHOOLPHYSICS WORKSHEET ON LIGHT

1. Binoculars are used to look at distant objects.

Many binoculars use right-angled prisms. The diagram shows two parallel rays of light, AB and FG, from a distant bird, incident on a right-angled prism.

(a) (i) On the diagram, draw the normal at G.(ii) Measure the angle of incidence at G and the angle of refraction at D.(b) Explain what happens to the light ray at C.(c) Complete the diagram by drawing the path that light ray FG takes through the prism.(jan 2017 p1)2.A light ray can undergo total internal reflection.a)i)What is meant by the term total internal reflection?ii)State two uses of total internal reflection.b)The diagram shows a light ray entering a glass block and travelling towards point O.

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The angle i is 25°.The critical angle of the glass is 42°.i)Which path does the ray take after reaching point O?

ii)State the equation linking critical angle and refractive index.iii)Calculate the refractive index of the glass. (may 2015 p1)3. A ray of light enters a glass block and is refracted as shown in fig 1.

a)Explain why the ray of light is refracted towards the normal.b)Opals and diamonds are transparent stones used in jewellery.Jewellers shape the stones so that light is reflected inside.Fig 2 shows the path of a ray of light that enters and leaves a shaped piece of opal.This ray of light is totally internally reflected.

i)State the equation linking refractive index and critical angle.

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ii)The critical angle of opal is 43°.Show that the refractive index is about 1.5.iii)The refractive index of diamond is 2.4.Explain why rays of light inside a diamond are more likely to be totally internally reflected than those inside an opal.(may 2013 p1)4. Pepper’s Ghost is a theatre effect used to make it appear that there is an image on stage.The diagram shows a theatre viewed from above.A sheet of glass is placed on the stage. A brightly lit actor stands behind a curtain atthe side of the stage.The audience sees the reflection of this actor in the glass.

(a) Add a ray diagram to show how light from the actor appears to come from the image.(b) The image formed by the glass is a virtual image.State what is meant by the term virtual image.(jan 2014 p15. A student uses a semicircular glass block to investigate refraction in glass.(a) List three other pieces of equipment that he needs for this investigation.(b) He shines a ray of light into the block at point P, as shown.P is the middle of the flat surface.

(i) On the diagram, draw the normal at P.

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(ii) Measure the angle of incidence and the angle of refraction.(iii) Explain why the ray of light changes direction at P.(c) The student varies the angle of incidence and obtains this table of results.

(i) Plot a graph of sin i against sin r.

(ii) Draw the straight line of best fit.

(iii) State the relationship between refractive index, angle of incidence and angle of refraction.(iv)Use your graph to find the refractive index of glass.

(may 2016 1pr)

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6. A student watches a demonstration of the total internal reflection of light in a semicircular glass block.

(a) He takes notes, but some of his notes are wrong.

Place a tick(√) or a cross (x) in the table to show which statements are right orwrong.The first statement is right and has been done for you.

(b) Jewellers cut jewels so that total internal reflection is more likely.Light enters a jewel along the normal AB and leaves along the normal CD as shown.Between B and C there are two total internal reflections.

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Complete the path of the light through the jewel.

(c) (i) Show, by calculation, that the critical angle for a refractive index of 1.5 is about 42°.

(ii) Explain why the quantity called refractive index has no unit.

(d) The graph shows how critical angle varies with refractive index.(i) Add the point (1.5, 42°) to the graph.

(ii) How can you tell that the point (1.5, 42°) is not anomalous?

(iii) Suggest two reasons why the axes of the graph do not start from zero.

(june 2016 p1)

7. (a) Which diagram shows the reflection of a ray of light at a plane mirror?

(b) The diagram below shows a ray of light as it passes from air into a glass block.

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The angle of incidence is 43° and the light is refracted as shown.

(i) On the diagram, draw the normal for this refraction.(ii) On the diagram, mark the angle of refraction.(iii) Measure the angle of refraction.

(iv) State the relationship between refractive index, angle of incidence and angle of refraction.(v) Calculate the refractive index of the glass.

(c) The diagram shows how light can travel in a glass fibre.

(i) What is the name given to the effect shown? (ii) Explain what is happening to the light in the glass fibre.(Jan 2016 p1)

8. A student plans to measure the refractive index of glass.She traces a ray of light through a glass block as shown in the diagram.

(a) Which letter represents the angle of refraction?

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(b) Explain how the student can use the glass block to find an accurate value for therefractive index of glass.

(jan 2015 p1)

9. (a) A student investigates refraction of light by using a salt solution in a hollow prism. He shines a ray of blue light from A to B and traces the path of the ray through the prism. The diagram shows the path of the ray of blue light.

(i) Explain what is meant by the term refraction.

(ii) On the diagram, draw the normal at B and measure the angle of incidence.

(iii) The student then shines a ray of red light from A to B. The refractive index of the salt solution is lower for red light than it is for blue light. On the diagram, sketch a possible path for the red light through the solution and out of the prism.

(iv) Suggest what would happen to the path of the blue light if the student used a salt solution with a higher refractive index.

(b) A technician working in a soft drinks factory uses refraction of light to measure sugar concentration in drinks. She takes readings using a refractometer. Different sugar concentrations give different scale readings on the refractometer. The table shows her results.

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(i) Plot a graph of the refractometer reading against sugar concentration and draw the curve of best fit.

(ii) Circle the anomalous point on your graph and suggest what the correct refractometer reading should be.

(iii) Use your graph to find the sugar concentration when the refractometer reading is 80.

(iv)Describe the pattern shown by your graph.

(may 2014 1pr)

10. A student investigates refraction using a glass block. She wants to find the refractive index of the glass. She sends rays of light into the block at different angles and measures the angle of incidence and the angle of refraction.

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The table shows her results.

(a) (i) Complete the table by calculating the missing values of sin r.

(ii) Draw a graph of sin i (y-axis) against sin r (x-axis).

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iii) Use your graph to find the refractive index of the glass.

(b) Suggest two reasons why using a graph to find the refractive index is a better method than simply calculating it using a pair of angles from the table.

(june 2014 2p)

11. (a) A student wants to find the refractive index of a glass block.

(i) Draw a diagram to show how the student should set up the apparatus needed to find the refractive index of a glass block. Label your diagram.

(ii) What measurements should the student take to find the refractive index of the glass block?

(iii) Describe how the student should use these measurements to find the refractive index of the glass block.

(b) The diagram shows a section through a bicycle reflector. A ray of light is incident on the flat surface of the reflector.

(i) The critical angle for the plastic of the reflector is less than 45°. Continue the incident ray on the diagram to show the path of the ray until it emerges from the plastic.

(ii) What happens to the incident ray as it enters the plastic?

(jan 2014 2p)

12. The diagram shows one of two 45°prisms used in an optical instrument. The second prism is not shown. The path of a ray of light is partly shown.

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(june 2013 1pr)

13. This question is about the reflection of light.

(a) Light reflects from a plane mirror.

(i) Use words from the box to complete the sentence below.

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(jan 2013 p1)

14. The diagram shows a light ray passing though a semicircular block of glass.

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(june 2012 p1)

15. A student uses a rectangular glass block to determine the refractive index of glass. The diagram shows a ray of red light in air as it enters the glass block at P. The normal at P is shown as a dotted line.

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(june 2012 p2)

16. A student is investigating refraction of light.

(a) What is refraction?

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(jan 2012 p1)

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