cbse-wizard

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  8. Class V

Chapter 15: Light

Q1. Complete the sentences by filling the blanks with appropriate words:(a)___ lens forms an image that cannot be obtained on a screen.(b) A ___ mirror always forms an image that is of the same size as the object.(c)A convex ____ always forms an image that is virtual and ____ in size.d) A___ image is an image that can be obtained on the screen.(e) ____ is an image that cannot be obtained on a screen.ANSWER:(a) Concave. (b) plane. (c) mirror (d) real (e)Virtual image.Q2. State whether the following statements are true or false.(a) Real images can be obtained on a screen.(True/ False)(b) Concave mirrors always produce a real image.(True/False)(c) Convex mirrors produce an erect and enlarged image.(True /False)(d) Concave mirrors produce an enlarged, inverted and a real image.(True/False)(e) We obtain a virtual image from a concave lens.(True/False)ANSWER:(a) True(b) False(c) False(d) True(e) True Q3. Match the columns.
Column 1Column 2
(a) Convex lens(i)an erect image which is of the same size as the object
(b) Concave lens(ii)magnifying glass
(c) Plane mirror(iii)an erect image that is smaller than the object.
(d) Convex mirror(iv)used by dentists.
(e) Concave mirror(v) image spreads over a large area
ANSWER:(a) – (ii)(b) – (ii)(c) – (i)(d) – (v)(e) – (iv)Q4. Write the characteristics of an image that a plane mirror forms.ANSWER: A plane mirror forms an image with the following characteristics:(i) It is an erect image.(ii) It is a virtual image.(iii) It is at the same distance from the mirror as the object is in front of the mirror.(iv) It is a laterally inverted image.(v) It is of the same size as the object.Q5. Write down the letters of the English alphabet whose images in a plane mirror appear same as the alphabet itself. Are the images not getting inverted? Discuss.ANSWER: The letters of the English alphabet whose images appear exactly like the alphabet are M,O,A,I,W,V,H,T,U etc.The images are getting inverted (laterally) but since these alphabets are perfectly symmetrical (vertically) the inversion does not affect the appearance.Q6. What do you understand by a virtual image? Provide a case where a virtual image is produced.ANSWER: A virtual image is an image that cannot be obtained or formed on a screen. The image of us formed on a plane mirror cannot be obtained on a screen, because this is a virtual image.Q7. Differentiate between convex and concave lens.ANSWER:
Convex LensConcave lens
i) It converges light.It diverges light.
ii)It is thicker in around the middle.It is slimmer and thinner around the middle.
Q8. State a use each of concave and convex mirror.ANSWER: Convex mirrors are used in roads and large buildings to allow people to see what is around the bend.Concave mirrors are used in reflecting telescopes and also as a magnification tool.Q9. Which mirror forms a real image?ANSWER: Concave mirrors form a real image.Q10. Which lens forms a virtual image?ANSWER: Concave lens produces a virtual image.Q11. A_____ mirror produces a virtual image which is larger than the object.ANSWER: Concave.Q12. Tyrion Lannyster is standing 4m in front of the mirror. If he steps one 1m back, what will the distance be between Tyrion and his image in the mirror?ANSWER: If Tyrion steps one meter back from his original distance of 4m from the mirror, then the distance between him and his image is 10m. It is so because in a plane mirror the image formed is at the same distance behind the mirror as the object in front of it. Q13. A car has a plane mirror as a rearview mirror. Mr.Wayne is reversing his car at a speed of 5m/s. He sees in his mirror that Robin’s bike is parked behind his car. What is the speed in which he will see the bike approach in his mirror?ANSWER: In a plane mirror the distance between the image and the object is doubled, so the speed of the approaching image is also doubled. Hence, Mr. Wayne sees the bike approach at a speed of 10m/s.