Assignment- Ray Optics, Class 10, Science PDF Download

Questions

1. An object is placed in front of a plane mirror. If the mirror is moved away from the object through a distance x, by how much distance will the image move

2. A ray of light falls on a plane mirror. Show that if the mirror is tilted through an angle q, the reflected ray tilts through an angle 2q.

3. A 2cm high object is placed at a distance of 32cm from a concave mirror. The image is real, inverted and 3cm in size. Find the focal length of the mirror and the position where the image is formed.

4. A ray of light travelling in air falls on the surface of a glass slab. The ray makes an angle of 45° with the normal to the surface. Find the angle made by the refracted ray with the normal within the slab. Refractive index of glass = 3/2.

5. Yellow light of wavelength 590 nm travelling in air is refracted into water . Find the wavelength of this light in water.

6. A cube of edge 6 cm is placed over a printed page. At what distance from the top surface of the cube will be letters appear when seen from above ? Refractive index of glass = 1.5.

7. An object is placed on the principal axis of a concave lens at a distance of 20 cm from it. If the focal length of the lens is also 20 cm, find the location of the image.

8. A beam of light travelling to the principal axis of a concave lens appears to diverge from a point 20 cm behind the lens after passing through the lens. Find the power of the lens.

9. A convex lens of power 4D is placed at a distance of 40 cm from a wall. At what distance from the lens should a candle be placed so that its image is formed on the wall ?

10. A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 12.5 cm in such a way that they have the same principal axis. Find the power of the combination.

11. A convex mirror used for rear-view on an automobile has a radius of curvature of 3.00 m. If a bus is located at 5.00 m from this mirror, find the position, nature and size of the image.

12. An object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image ? Find the nature and the size of the image.

13. A concave lens has focal length of 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens ? Also, find the magnification produced by the lens.

14. A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the image. Also find its magnification.

15. An object placed in front of a diverging mirror at a distance of 30 cm, forms a virtual and erect image which is 1/5 of the size of the object. Calculate : (i) the position of the image, (ii) the focal length of the diverging mirror.

16. A light of wavelength 500 nm in air enters a glass block of refractive index 1.5. Find (a) speed; (b) frequency; (c) wavelength of light in glass. Velocity of light in air is 3 × 10⁸ m/s.

17. Consider a system of two plane mirror inclined to each other at a right angle. Show that when a ray of light is incident on the system, the outgoing ray is parallel to the incident ray and this result is independent of the incident direction.

18. A near sighted person wears eye glass with power of  -5.5D for distant vision. His doctor perscribes a correction of +1.5D in near vision section of his bifocals, which is measured relative to main part of the lens.

(i) What is the focal length of his distant viewing part of lens ?

(ii) What is the focal length of near vision section of the lens ?

19. The radius of curvature of a convex mirror used on a moving automobile is 2.0 m. A truck is coming behind it at a constant distance of 3.5 m. Calculate (i) the position, and (ii) the size of image relative to the size of the truck. What will be the nature of the image ?

20. The refractive index of dense flint glass is 1.65, and for alcohol, it is 1.36 with respect to air. What is the refractive index of the dense flint glass with respect to alcohol ?

21. A convex lens forms a real and inverted image of a needle at a distance of 50 cm from the lens. Where is the needle placed in front the convex lens, so that this image is of the same size as the object ? Also, find the power of the lens.

22. A person can not see objects distinctly at distances less than 1 m. Calculate the power of the spectacles lens that he should use in order to read a book at a distance of 25 cm.

23. Name the type of mirror used in the following situations :

(a) Head lights of a car.

(b) Side rear view mirror of a vehicle.

(c) Solar furnace.

Support your answer with reason.

24. What kind of lens can form a (i) Virtual, erect, diminished image? (ii) virtual, erect, magnified image?

25. Which lens has greater power, a convex lens of focal length 10 cm or a convex lens of focal length 20 cm?

26. A man standing in front of a special mirror finds his image having a small face, big tummy and legs of normal size. What are the shapes of three parts of the mirror?

27. Can you change focal length of a given spherical mirror by changing the object distance from the mirror?

28. Can you change linear magnification of a spherical mirror by changing the object distance from the mirror?

29. What is the basic cause of refraction?

30. What are the conditions for no refraction of light?

31. A concave mirror is used as a head mirror by ENT specialists. The same mirror can also be used as a shaving mirror. Why?

ANSWER KEY

1. 2x 3. f = _19.2 cm, v = _48 cm 4. 28° 5. 442.5 nm 6. 4 cm 7. -10 cm 8. -5D 9. _cm

10. -3D 11. 1.15 m, +0.23 12. -37.5 m, -6.0 cm 13. -30 cm, +0.33 14. +30 cm, -4.0 cm, m = -2

15. (i) 6 cm (ii) 7.5 cm 16. (a) 2 × 10⁸ m/s (b) Same (c) 333.3 nm

18. (i) -18.18 cm (ii) -25 cm 19. (i) 0.78 m (ii) 0.22 20. 1.21 21. -50 cm, 4 D 22. +3 D

VERY SHORT ANSWER QUESTIONS (CARRYING 1 MARKS EACH)

1. If the magnification of a body of size 1 m is 2, what is the size of the image ? (2003)

2. What is the power of a concave lens of focal length 25 cm ? (2004)

3. What will be the focal length of a lens whose power is given as +2.0 D ? (2004)

4. Where will the image be formed by a concave mirror when an object is placed between the pole and the focus point of the mirror ? (2005)

5. What is the value of focal length of a plane mirror ? (2005)

6. A ray of light is incident on a convex mirror as shown in fig. Redraw the above diagram after completing the path of the light ray after reflection from the mirror. (2006)

7. Copy fig. in your answer book and show the direction of the light ray after reflection. (2008)

8. The refractive index of diamond is 2.42. What is the meaning of this statement in relation to speed of light ?

(2008)

9. Draw fig. in your answer book and show the formation of image of the object AB with the help of suitable rays.

10. Draw fig. in your answer book and show the formation of image of the object AB with the help of suitable rays.

11. Draw fig. in your answer book and show the formation of image with the help of suitable rays.

SHORT ANSWER QUESTIONS (CARRYING 2 MARKS EACH)

12. Give the characteristics of image formed by a plane mirror. (2003)

13. An object is placed at 0·06 m from a convex lens of focal length 0·1 m. Calculate the position of the image?

14. An object is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position and nature of the image. (2004)

15. Light enters from air into diamond, which has a refractive index of 2.42. Calculate the speed of light in diamond. The speed of light in air is 3 × 10⁸ ms^_1. (2005)

16. With the help of ray diagrams, show the formation of the images of an object by a concave mirror. When it is placed (i) beyond the centre of curvature (ii) at the centre of curvature. (2005)

17. Draw ray diagrams to show the formation of image of an object by a concave mirror, when it is placed (i) between its centre of curvature C and focus F (ii) between pole P of mirror and its focus F. (2005)

18. With respect to air, the refractive index of ice is 1·31 and that of rock salt is 1·54. Calculate the refractive index of rock salt w.r.t. ice. (2005)

19. Draw ray diagrams to show the formation of image of an object by a concave lens when the object is placed.
(i) at infinity (ii) between infinity and optical centre of the lens. (2005)

20. Draw a ray diagram to show the position and nature of the image formed when an object is placed between focus F and pole P of a concave mirror. (2006)

21. Draw ray diagrams to show the formation of the image of an object by a convex mirror, when it is placed
(i) at infinity and (ii) between infinity and pole of the mirror. (2006)

22. Draw a labelled ray diagram to locate the image of an object formed by a convex lens of focal length 20 cm when the object is placed 20 cm away from the lens.

23. Explain with the help of a diagram, why a pencil partly immersed in water appears to be bent at the water surface. (2008)

24. Draw the ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed (i) at 2 F₁ (ii) between F₁ and optical centre O of the lens. (2008)

SHORT ANSWER QUESTIONS (CARRYING 3 MARKS EACH)

25. Calculate the distance at which an object should be placed in front of a thin convex lens of focal length 10 cm to obtain a virtual image of double its size. (2003)

26. A convex lens of focal length 40 cm is placed in contact with a concave lens of focal length 25 cm. What is the power the combination ? (2003)

27. Find the position of an object, which when placed in front of a concave mirror of focal length 20 cm produces a virtual image, which is twice the size of the object. (2003)

28. A concave lens made of a material of refractive index n₁ is kept in a medium of refractive index n₂. A parallel beam of light is incident on the lens. Complete the path of rays of light emerging from the concave lens if
(i) n₁ > n₂ (ii) n₁ = n₂ (iii) n₁ < n₂. (2003)

29. Find the position, nature and size of the image formed by a convex lens of focal length 20 cm of an object 4 cm high placed at a distance of 30 cm from it. (2004)

30. A convex lens has focal length of 30 cm. Calculate at what distance should the object be placed from the lens so that it forms an image at 60 cm on the other side of the lens ? Find the magnification produced by the lens in this case. (2004)

31. Find the option, nature and size of the image of an object 3 cm high placed at a distance of 9 cm from a concave of focal length 18 cm. (2004)

32. An object 4 cm high is placed 40-0 cm in front of a concave mirror of focal length 20 cm. Find the distance from the mirror, at which a screen be placed in order to obtain a sharp image. Also find the size and nature of the image formed. (2005)

33. An object is placed at a distance of 12 cm in front of a concave mirror. It forms a real image four times larger than the object. Calculate the distance of the image from the mirror.

34. A 5.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal 20 cm. The distance of the object from the lens from the lens is 30 cm. By calculation, determine (i) the position (ii) the size of the image formed.

35. An object 30 cm high is placed perpendicular to the principal axis of a concave lens of focal length 7.5 cm. The image is formed at a distance of 5.0 cm from the lens. Calculate (i) distance at which object is placed, and (ii) size and nature of image formed. (2006)

36. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens ? Also, calculate the size of the image formed. (Delhi, 2007)

37. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. (2007)

LONG ANSWER QUESTIONS (CARRYING 5 MARKS EACH)

38. Draw ray diagrams to show the formation of images when the object is placed in front of a concave mirror

(i) between its pole and focus point.

(ii) between the centre of curvature and focus point.

39. (a) State the relation between object distance, image distance and focal length of a spherical mirror.

(b) Draw a ray diagram to show the image formed by a concave mirror when an object is placed between pole and focus of the mirror.

(c) A concave mirror of focal length 15 cm forms an image of an object kept at a distance of 10 cm from the mirror. Find the position, nature and size of the image formed by it.