Light important Question Reflection and Refraction Class 10

Important question for chapter -Light Reflection and Refraction for class 10. Previous years PYQ for Chapter Light Reflection and Refraction for class 10.

Important question Light Reflection and Refraction -2020

1. The laws of reflection hold true for:                [2020]
   • concave mirrors only
   • all reflecting surfaces
   • plane mirrors only
   • convex mirrors only
2. When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. This image is:                                                                           [2020]
   • A security mirror used in a big showroom has radius of curvature 5 m. If a customer is standing at a distance of 20 m from the cash counter, find the position, nature and size of the image formed in the security mirror.
   • Neha visited a dentist in his clinic. She observed that the dentist was holding an instrument fitted with a mirror. State the nature of this mirror and reason for its use in the instrument used by dentist.[2020]
3. Rishi went to a palmist to show his palm. The palmist used a special lens for this purpose.
   • State the nature of the lens and the reason for its use.
   • Where should the palmist place/hold the lens so as to have a real and magnified image of an object?
   • If the focal length of this lens is 10 cm and the lens is held at a distance of 5 cm from the palm, use lens formula to find the position and size of the image.[2020]
4. Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:
   • between the optical center and principal focus of a convex lens.
   • anywhere in front of a concave lens.
   • at 2F of a convex lens.
   • State the signs and values of magnifications in the above-mentioned cases (i) and (ii).[2020]
5. An object 4.0 cm in size, is placed 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 size of the image.
   • Draw a ray diagram to show the formation of an image in this case.[2020]
6. Draw a labelled ray diagram to show the path of a ray of light incident obliquely on one face of a glass slab.
   • Calculate the refractive index of the material of a glass slab. Given that the speed of light through the glass slab is 2 × 10⁸ m/s and in air is 3 × 10⁸ m/s.
   • Calculate the focal length of a lens, if its power is – 2.5 D.

Important question Light Reflection and Refraction -2019

1. A student holding a mirror in his hand, directed the reflecting surface of the mirror towards the Sun. He then directed the reflected light on to a sheet of paper held close to the mirror.
   • What should he do to burn the paper?
   • Which type of mirror does he have?
   • Will he able to determine the approximate value of focal length of this mirror from this activity? Give reason and draw ray diagram to justify your answer in this case.[2019]
2. List four characteristics of the images formed by plane mirrors.
3. A 5 cm tall object is placed at a distance of 20 cm from a concave mirror of focal length 30 cm. Use mirror formula to determine the position and size of the image formed.[2019]
4. A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 18 cm. Find the nature, position and size of the image formed.[2019]
5. What is atmospheric refraction? Explain with the help of a labelled diagram that the position of a star as seen by us is not its true position.[2019]
6. List four precautions which a student should observe while determining the focal length of the given convex lens by obtaining image of a distant object on a screen.[2019]
7. List in proper sequence the steps of the experiment for determining the approximate focal length of a given concave mirror by obtaining the image of a distant object.[2019]
8. An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm.
   • Use the lens formula to find the distance of the image from the lens.
   • List four characteristics of the image (nature, position, size, erect/inverted) formed by the lens in this case.
   • Draw a ray diagram to justify your answer to the part(ii).[2019]
9. Draw the path of a ray of light when it enters one of the faces of a glass slab at an angle of nearly 45°. Label on it.
   • angle of refraction,
   • angle of emergence and
   • lateral displacement.[2019]
10. What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.[2019]
11. A student has to trace the path of a ray of light passing through a rectangular glass slab for four different values of angle of incidence.
    • Write two important precautions for this experiment.
    • List two conclusions the student will draw based on his experiment.[2019]

Important question Light Reflection and Refraction -2018

Important question Light Reflection and Refraction -2017

Important question Light Reflection and Refraction -2016

1. Draw a ray diagram to show the refraction of light through a glass slab and mark an angle of refraction and the lateral shift suffered by the ray of light while passing through the slab.
2. If the refractive index of glass for light going from air to glass is 3/2, find the refractive index of air for light going from glass to air.[2016]
3. “The magnification produced by a spherical mirror is -3.” List four information you obtain from this statement about the mirror/image.[2016]
4. A divergent lens has a focal length of 20 cm.
   • At what distance should an object of height 4 cm from the optical centre of the lens be placed, so that its image is formed 10 cm away from the lens.
   • Find the size of the image also.
   • Draw a ray diagram to show the formation of image in above situation.[2016, 2012]
5. What is meant by power of a lens? What does its sign (+ve or – ve) indicate? State its SI unit. How is this unit related to focal length of a lens?[2016]
6. Define focal length of a spherical lens.
   • A divergent lens has a focal length of 30 cm. At what distance should an object of height 5 cm from the optical centre of the lens be placed, so that its image is formed 15 cm away the lens? Find the size of the image also.
   • Draw a ray diagram to show the formation of image in the above situation.[2016]
7. Draw a ray diagram to show the formation of image by a convex lens when an object is placed in front of the lens between its optical centre and principal focus.
   • In the above ray diagram mark the object distance (u) and the image distance (v) with their proper signs (+ ve or – ve as per the new cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.
   • Find the power of convex lens which forms a real and inverted image of magnification -1 of an object placed at a distance of 20 cm from its optical centre.[2016]
8. It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm.
9. What should be the range of distance of an object placed in front of the mirror?
10. Will the image be smaller or larger than the object? Draw ray diagram to show the formation of image in this case.
11. Where will the image of this object be, if it is placed 24 cm in front of the mirror? Draw ray diagram for this situation also to justify your answer. Show the positions of pole, principal focus and the centre of curvature in the above ray diagrams.[2016]

Important question Light Reflection and Refraction -2015

1. One half of a convex lens of focal length 10 cm is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of 30 cm from the lens? Draw a ray diagram to justify your answer.
2. A 4 cm tall object is placed perpendicular to principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 15 cm. Find the nature, position and the size of the image.[2015]
3. What is meant by power of a lens? Define its SI unit.
4. You have two lenses A and B of focal lengths +10 cm and – 10 cm, respectively. State the nature and power of each lens. Which of the two lenses will from a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer.[2015]
5. A student has three concave mirrors A, B and C of focal lengths 20 cm, 15 cm and 10 cm, respectively. For each concave mirror, he performs the experiment of image formation for three values of object distance of 30 cm, 10 cm and 20 cm.
   Give reasons for the following:
   • For the three object distances, identify the mirror which will form an image equal in size to that of object. Find at least one value of object distance.
   • Out of the three mirrors, identify the mirror which would be preferred to be used for shaving purpose.
   • For the mirror B, draw ray diagram for image formation for any two given values of object distance.[2015]

Important question Light Reflection and Refraction -2014

1. A student wants to project the image of a candle flame on a screen 48 cm in front of a mirror by keeping the flame at a distance of 12 cm from its pole.
   • Suggest the type of mirror he should use.
   • Find the linear magnification of the image produced.
   • How far is the image from its object?
   • Draw a ray diagram to show the image formation in this case.[2014]
2. A spherical mirror produces an image of magnification -1 on a screen placed at a distance of 50 cm from the mirror.
   • Write the type of mirror.
   • Find the distance of the image from the object.
   • What is the focal length of the mirror?
   • Draw the ray diagram to show the image formation in this case.[2014]
3. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. where should be the position of object ?Justify your answer .[2014]
4. A student wants to project the image of a candle flame on the walls of the school laboratory by using a mirror.
   • Which type of mirror should he use and why?
   • At what distance, in terms of focal length f of the mirror, should he place the candle flame to get the magnified image on the wall?
   • Draw a ray diagram to show the formation of the image in this case.
   • Can he use this mirror to project a diminished image of the candle flame on the same wall State ‘how’, if your answer is ‘yes’ and why not’, if your answer is ‘no’.[2014]
5. A student wants to project the image of a candle flame on the walls of school laboratory by using a lens.
   • Which type of lens should he use and why?
   • At what distance in terms of focal length F of the lens should he place the candle flame, so as to get
     1. a magnified and 
     2. a diminished image respectively, on the wall?
   • Draw ray diagrams to show the formation of the image in each case. [2014]

Important question Light Reflection and Refraction -2013

Important question Light Reflection and Refraction -2012

1. An object 1 cm high produces a real image 1.5 cm high when placed at a distance of 15cm from a concave mirror.
   • Calculate the position of the image and the magnification.
   • Write two uses of concave mirrors [2012]
2. In refraction of light through a rectangular glass slab, the emergent ray is parallel to the direction of the incident ray. Why?
3. What happens when a light ray is incident normally on one of the faces of a rectangular glass slab? [2012]
4. Name the type of mirror used in a solar furnace. How can high temperature be achieved by this device?[2012]
5. An object is kept at a distance of 100 cm from each of above lenses. Calculate
   • image distance and
   • magnification in each of the two cases.[2012]
6. Define optical centre of spherical lens.
7. A divergent lens has a focal length of 20 cm.
   • At what distance should an object of height 4 cm from the optical centre of the lens be placed, so that its image is formed 10 cm away from the lens.
   • Find the size of the image also.
   • Draw a ray diagram to show the formation of image in above situation.[2016, 2012]
8. What should be the position of an object with respect to focus of a convex lens of focal length 20cm, so that its real and magnified image is obtained?[2012]
9. A dentist uses a mirror in front of a decayed tooth at a distance of 4 cm from the tooth to get a four times magnified image in the mirror. Use mirror formula to find the focal length and nature of the mirror used.[2012]
10. A ray of light strikes the glass slab at an angle of 90∘. What are the angle of incidence and the angle of refraction?[2012]
11. When two or more lenses are placed in contact, what will be their combined power?[2012]
12. For the same angle of incidence in medium P, Q and R, the angles of refraction are 45⁰, 35⁰ and 15⁰ respectively. In which medium will the velocity of light be minimum? Give the reason for your answer.[2012]
13. The radius of curvature of a concave mirror is 50 cm. Where should an object be placed from the mirror, So as to form its image at infinity? Justify your answer.[2012]
14. A ray of light incident on one face of a rectangular glass slab emerges from the opposite face of the slab parallel to the direction of the incident ray. Why does it happen so?[2012]
15. A ray of light travelling from a medium X enters obliquely into another medium Y. If it bends away from the normal, then state which one of the two is relatively optically denser. Why?[2012]

Important question Light Reflection and Refraction -2011

1. For what position of an object, a concave mirror forms a real image equal in size to the object?[2011]
2. Why is the refractive index of atmosphere different at different altitudes?[2011]
3. If the speed of light in a medium is 2/3 rd of the speed of light in vacuum, find the refractive index of that medium.[2011]
4. A ray passing through the centre of  curvature of a spherical mirror after reflection, returns along the same path. Why?[2011]
5. What should be the position of the object when a concave mirror is to be used
   1. as a shaving mirror and 
   2. in torches producing parallel beam of light? 
6. A man standing in front of a mirror, finds his image having a very small head and legs of normal size. What type of mirrors are used in designing such a mirror?[2011]
7. How can you distinguish between plane mirror, convex mirror and concave mirror by merely looking at the image formed in each case?[2011]
8. Why does a ray of light bend when it travels from one medium into another?[2011]