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Feb 19

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Class X Physics :: LIGHT : REFLECTION AND REFRACTION :: Question Bank

1. What are the characteristics of image formed by a plane mirror?
2. Where an object should be placed in front of a concave mirror so as to get unit magnification?
3. Define pole of a spherical mirror.
4. Name the type of spherical mirror used by a dentist to see the teeth of a patient clearly.
5. A beam of light parallel to the principal axis of a concave mirror converges to a point. What is the point called? Draw a diagram to illustrate it.
6. Draw a diagram to show the transmission of light when the angle of incidence at the surface of separation between two transparent media is zero degree.
7. What is lateral displacement?
8. Draw neat labelled diagram to show the formation of image by a concave mirror when an object is placed at a point
1. Beyond centre of curvature
2. At centre of curvature
3. Between F and C
4. At F
5. Between F and P. Also write the characteristics of image formed in each case.
9. Draw neat labelled diagram to show the formation of image by a convex lens when an object is placed at a point

1. Beyond 2F
2. At 2F
3. Between F and 2F
4. At F

5. Between F and P. Also write the characteristics of image formed in each case.
10. Write the sign conventions for a spherical lens.
11. Draw a neat labeled diagram to show lateral displacement when light is passed through a rectangular glass slab
12. An object of height 8.0 cm is placed at 50 cm in front of a concave mirror of focal length 30 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Also find the nature and size of image.
13. Write any two typical rays chosen to locate the image formed by a concave mirror.
14. Define real image and virtual image.

15. When an object is kept beyond the centre of curvature of a concave mirror, what is the nature of image formed?

16. An object is placed at a distance of 10cm from a convex lens of focal length 15 cm. Find the position size and nature of image formed.

17. What is lateral inversion?

18. Write any 4 uses of a plane mirror.

19. Define centre of curvature, radius of curvature, pole and principal axis of a spherical mirror.

20. Define principal focus of a

a. Concave mirror

b. Convex mirror

c. Convex lens and

d. Concave lens

21. What is the relation between the radius of curvature and focal length of a spherical mirror?

22. Write any 3 uses of a concave mirror.

23. With the help of ray diagram explain the uses of convex mirror.

24. Write mirror formula and explain the terms involved.

25. Define magnification of a mirror.

26. A rear view mirror used in a bus has a radius of curvature 3.5 m. If the driver of the bus locates a car at 10.0m behind the bus, find the position, nature and size of the image of the car.

27. What is the focal length of a plane mirror?

28. An object 4cm high is placed at a distance of 6 cm in front of a concave mirror of focal length 12 cm. Find the position, nature and size of the image formed.

29. How far an object should be placed from the pole of a concave mirror of focal length 20cm to form a real image whose size is 1/5 the size of the object.

30. What is diffused reflection?

31. State the laws of reflection

32. State the laws of refraction.

33. Why a convex mirror is used as the rear view mirror of a vehicle and not a plane mirror?

34. Define power of a lens. What is its unit? Define it.

35. A concave mirror is kept in water. Will there be any change in its focal length as compared to that in air?

36. What kind of a wave is light?

37. Define refractive index of a medium.

38. What is the minimum value of refractive index possible?

39. Light enters from air into glass plate which has a refractive index of 1.5. Calculate the speed of light in glass. (Given, speed of light in vacuum is 3 x 108ms-1

40. A convex lens has a focal length of 40 cm. Calculate its power.

41. List the physical quantities which remain constant when light travels from one medium to another.

NUMERICAL PROBLEMS

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

43. A concave lens has focal length 20cm. 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.

44. An object 2.0 cm in size is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance from the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed?

45. A convex lens has a 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.

46. 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 the image relative to the size of the truck. What will be the nature of the image?

47. 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.

48. A doctor has prescribed a corrective lens of power +1.2 D. Find the focal length of the lens to be used. Is the lens converging or diverging? What would be the defect of the eye?

49. A small candle 2.5 cm in size is placed 27 cm in front of a concave mirror of radius of curvature 0.36 m. At what distance from the mirror should a screen be placed in order to receive a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved to obtain sharp image?

50. A concave mirror of focal length 20 cm forms a real, inverted image of same size as that of the object. Where is the object placed with respect to the mirror? Draw a diagram to show the image formation?

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Comments

  1. prathibha says:

    it the help full for all thanks to you.

  2. apurva says:

    ple give me answers of these question

    1. admin says:

      It would be better if you try answering the questions yourself and ask your doubts here.

      1. Prasanjeet das says:

        Sir what is the answer for 6th question. :)

        1. admin says:

          Angle of incidence = 0 means that the incident ray is normal to the surface. (Remember that angle of incidence is the angle between incident ray and the normal)
          So, you have to draw the case when a ray of light is incident normal to the surface

  3. neena says:

    can you tell the answer of 49th question?

    1. neena says:

      plz answer the 49th question

      1. admin says:

        For the sake of convenience, I am repeating the question here:
        49. A small candle 2.5 cm in size is placed 27 cm in front of a concave mirror of radius of curvature 0.36 m. At what distance from the mirror should a screen be placed in order to receive a sharp image? Describe the nature and size of the image. If the candle is moved closer to the mirror, how would the screen have to be moved to obtain sharp image?
        Answer
        From the question, we can get

        u= – 27 cm
        f =r/2 = -18 cm
        v =?
        from the relation
        1/v + 1/u = 1/f
        we get v = -54 cm

        That is the screen should be placed at a distance of 54 cm from the mirror in order to get a sharp image.

        further,
        from the relation
        magnification m = -v/u = height of image /height of object
        on solving we get
        height of image = 5 cm
        Thus,
        The image formed is real inverted and magnified twice as the object

        If the candle is moved towards the mirror, the screen should be moved further away from the mirror so as to obtain a clear image.

        1. pratiksha says:

          i feel itz not rite….cuz in questn u hav givn tat candle is placed 27m in frnt of concave mirror
          but in the answer u hav solved it as u=-2.5
          whereas 2.5 is size of the object

          1. muskaan says:

            1/f=1/v+1/u
            1/v=1/18-1/27
            1/v=1/-54cm
            v=-54cm
            m=-v/u
            here we have got the values of u and v as -27cm and-54cm
            and its given that the size of object is 2.5 cm
            as we know m=height of the image/height of the object
            substituting ie.,
            m=54/-27=height of the image/2.5
            height of the image =2.5^-2=5cm hence the image is real and inverted and magnified twice as the object

          2. admin says:

            It was a typing error. But the solution is correct and used the correct figures only

    2. mano says:

      yes i can solve this question very easily

  4. athirarshanker says:

    a candle is kept infront of a plane mirror at a distance of 15cm.what is the distance between candle and its image?

    1. admin says:

      You know that a plane mirror forms an image which is the same distance behind the mirror as the object infron of it.
      If the candle is 15cm in front of the mirror, the image will be 15 cm behind the mirror. So the distance between the candle and its image will be (15 +15 =) 30 cm

    2. abhisha says:

      as u=v in a plane mirror
      answer would be 30cm

  5. Ramu says:

    answer to question 44 pls..

  6. Ramu says:

    pls answer the 44th question

    1. admin says:

      The Question was
      44. An object 2.0 cm in size is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance from the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed?

      f = -10.0 cm
      u = – 20.0 cm
      v = ?
      ho = 2 cm
      hi = ?
      from the relation
      1/u + 1/v = 1/f
      we get on solving
      v=-20 cm
      (Otherwise also we know that r = 2f (given, f = 10 and u=20 = 2 x 10) and if object is at C (at a distance = 2f=r), the mage is also formed at the same point and the same size but inverted)
      m = – v/u = hi/ho
      which gives
      hi = -2 cm
      ie, the image is real and formed at the same position as that of the image, it is of the same size, but it is inverted

    2. abhisha says:

      object height=2cm
      object distance= -20cm
      focal length= -10cm
      image distance=?
      image height=?
      1/v+1/u=1/f
      1/v+1/-20=1/-10
      1/v=1/-10+1/20
      1/v=1/20-1/10
      1/v=-1/20
      v= -20
      As u= -20,we can say that v=u and so object height= image height.so we can say that if we put the screen beneath centre of curvature,a sharp image will be obtained.
      NATURE:REAL AND VIRTUAL
      SIZE:SAME AS THAT OF THE OBJECT

  7. sonal says:

    answer to question45 plz……….

  8. vishal says:

    wht is the ans to the 41st question??

    1. admin says:

      Frequency and color of light remain constant when light travels from one medium to another

  9. das shankar says:

    wht is the answer of 2nd question

    1. admin says:

      unit magnification means image size = object size and this happens when object is at C (centre of curvature)

  10. TANYA says:

    Can I plz get answers to these questions I have tried all but want to check my answers

  11. TANYA says:

    Plz Can i get answers of all these ques.
    I've tried but want to check my answers

  12. nivedha says:

    h,ey dey seem 2 b a WONDERFUL COLLECTION of questions..nice site 4 students 2 test der talents..

  13. Ramalingam says:

    where should an object be placed in front of a concave mirror of focal length 20 cm so as to obtain an image two times magnified?

    1. muskaan says:

      i think this is the answer
      f=-20cm
      m=-v/u=hi/ho
      u=-v/2
      1/f=1/v+1/u
      1/f=1/v-2/v
      v=20cm
      so 20cm from the mirror

      1. Akshay jain says:

        sorry but i think u r wrong coz the focal lenth of a concave mirror is asked and u have taken it +ve
        it should be taken -ve

  14. payal says:

    plzzzzzzz answer da questions… its quite tough for children…

    1. admin says:

      Please post the questions which you find difficult to answer.

  15. monika says:

    answer for 50th question plzzzz………………plzzzzzzzzz…………………..fast……………………

  16. Akkkk says:

    When an object is kept at a distance of 60cm from a concave mirror, the magnification is 1/2. Where should the magnification be placed to get magnification of 1/3??

    plz ans this que…..

    1. admin says:

      Your question along with answer is posted at http://www.askphysics.com

  17. @ admin – U have solved q.49 in a wrong way..

    1. admin says:

      The solution is correct though there was a typing error. Still if you feel so, you are welcome to post the correct answer with detailed solutions

    2. rachita says:

      given f=-18 u=-27 ho=2.5 v=? 1/f=1/v+1/u so 1/v=1/f-1/u=-1/18-(1/-27)=-54 m=hi/ho=-v/u so hi=2.5*-(-54/-27)=-5 cm r u agree ?

  18. $$Navya$$ says:

    Could you please answer the 41st Q?

  19. $$Navya$$ says:

    sorry,i meant 42nd

  20. Vachan says:

    Should WE Take V Positive Or Negative In a Convex Lens ?

    1. admin says:

      v can be positive or negative for a convex lens. ie; if the image is real, v is + and if image is virtual, v is -ve

  21. _|911|_ Vinay (-_(-_-)_-) says:

    if you don’t mind can you help me with the quetion #42

  22. i like this al ques.will u giv me the ans.of the ques.

  23. vidisha says:

    thnxs…..its really helpful:D

  24. questions are good i have tried but its bad to say that there is no answer of these questions

  25. Rahul Tulani says:

    Thnxxx these are good questions for practicing….

  26. arjun says:

    plz tell what is the maximum distance between an image and object in case of concave and convex lens?????

  27. harshit says:

    post answers also

  28. kavya says:

    wow….. its so simple

  29. kavya says:

    wow…. its so simple…

  30. harshit says:

    yeah its simple but how will i know that my answer is right or wrong ??

  31. Prashant says:

    Can anyone plzzzz tell me d answer of 29th question

  32. Prashant says:

    Can anyone plzz tell me d answers of 29 question

  33. mano says:

    yes i can solve it in seconds.

  34. sharon says:

    ans to the 29 plz

  35. sathish says:

    scientist have discovered that dark energy is the fastest energy in the universe,,,,,but Einstein said that light in the fastest energy,,,what do you think about it ??

  36. sathish says:

    hi/ho = 2 what do you mean by this?

    1. admin says:

      Image is twice as magnified as the object

  37. sathish says:

    answer for 29th ,,i hope this is the correct ans………………………………………………………..f=-20
    hi=1/5 ho
    hi/ho=1/5
    so surely it is a diminished image since
    hi<ho
    so if the image is diminished in a concave mirror either the object must b at infinity or beyond c

    since ho is given a defined ratio …the object cant b at infinity,since at infinity the ho cant b measured

    so the object must b kept beyond c

  38. devesh says:

    it’s very helpful for me thanks……………

  39. Arun says:

    Pls answer que no 46

    1. admin says:

      f=r/2 = 1 m
      u=-3.5m
      v=?
      m=?
      1/u+1/v = 1/f
      1/v = 1/f-1/u = 1- (-1/3.5)=4.5/3.5
      => v = 3.5/4.5 =7/9 m
      m=-v/u =1/4.5=0.22
      So, a virtual erect and diminished image formed behind the mirror.

  40. Arun says:

    please somebody say me wats d magnification for 46

  41. riddhi says:

    m=0.22 for q 46

  42. sathish says:

    in solar furnaces concave mirrors r used,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,so the object is at infinity, and the image is at focus,,,,,,,,,,,,,,,so only spots will glow on solar panel then wat is the use of it?

  43. sharon says:

    post answers 4 these questions..

  44. sharon says:

    post answers 4 these questions.

  45. cooooooooooooooooooool……………!!!!!!!!!!!

  46. stranger says:

    ans for 42 nd question

  47. stranger says:

    ans of 43rd question

  48. stranger says:

    43rd ans

  49. Someone says:

    what is the formula for finding the magnification of lenses??? is it m= v/u =hi/ho ????????? i’m not so sure of it..is it right? :/

  50. rachita says:

    in q no 49 why the value of height of image came +ve while from m=-v/u &after putting value of v(-54)& u(-27)

  51. coolme says:

    can u tell me the answer to the 29th and 39th question?

  52. Umar Afridi says:

    y z minus(-) in mirror formula n plus (+) in lense formula?

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