Which of the following can make a parallel beam of light when light from a point source is incident on it?
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. The object must be:
The focal length of a concave mirror of radius of curvature 20 cm is:
A ray of light travelling in air enters obliquely into water. The light ray:
The magnification produced by a plane mirror is +1. This means the image is:
No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be:
The power of a convex lens of focal length 50 cm is:
Which of the following has the highest refractive index?
A spherical mirror and a thin spherical lens each have a focal length of -15 cm. The mirror and the lens are likely to be:
Where should an object be placed in front of a convex lens to get a real image of the same size as the object?
Name a mirror that can give an erect and enlarged image of an object. (2 marks)
Why do we prefer a convex mirror as a rear-view mirror in vehicles? (2 marks)
Find the focal length of a convex mirror whose radius of curvature is 32 cm. (2 marks)
A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located? (2 marks)
The refractive index of diamond is 2.42. What is the meaning of this statement? (2 marks)
You are given kerosene, turpentine and water. In which of these does light travel fastest? (Refractive indices: kerosene 1.44, turpentine 1.47, water 1.33) (2 marks)
Define 1 dioptre of power of a lens. (2 marks)
What is meant by the magnification produced by a spherical mirror? What do a positive and a negative sign of magnification indicate? (2 marks)
Why does a ray of light bend when it travels from one medium into another? (2 marks)
Distinguish between the images formed by a convex lens when the object is placed beyond 2F1 and between F1 and the optical centre. (2 marks)
An object is placed at a distance of 12 cm in front of a convex mirror of focal length 18 cm. Find the position, nature and magnification of the image. (3 marks)
An object 2 cm tall is placed at 15 cm in front of a convex lens of focal length 10 cm. Find the position, size and nature of the image. (3 marks)
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. (3 marks)
A ray of light travels from air into a medium in which its speed is 2.25 x 10^8 m/s. Find the refractive index of the medium. Which common liquid could it be? (Speed of light in air = 3 x 10^8 m/s) (3 marks)
An object of height 6 cm is placed perpendicular to the principal axis of a concave lens of focal length 5 cm. If the distance of the object from the optical centre is 10 cm, find the position, size and nature of the image. (3 marks)
Read the passage and answer the questions. A dentist uses a small concave mirror of focal length 2 cm to examine a patient's teeth. She holds the mirror 1.5 cm from a tooth so that she sees an enlarged image. (i) Where is the tooth relative to the focus of the mirror? (ii) Using the mirror formula, find the position of the image. (iii) Find the magnification and state the nature of the image. (5 marks)
Read the passage and answer the questions. At a traffic junction, a convex mirror is fixed at a blind turn so that drivers can see vehicles coming from the other road. The mirror has a focal length of 1 m, and a car is 9 m away from it. (i) Find the position of the image of the car. (ii) Find the magnification and describe the image. (iii) Why is a convex mirror preferred here over a plane mirror? (5 marks)
Read the passage and answer the questions. In a physics lab, students look at a coin placed at the bottom of a beaker. When water is poured into the beaker, the coin appears to rise. The refractive index of water is 1.33. (i) Name the phenomenon responsible. (ii) Why does the coin appear raised? (iii) If the speed of light in air is 3 x 10^8 m/s, find its speed in water. (5 marks)
Read the passage and answer the questions. A student wants to obtain a sharp image of a distant tree on a screen using a convex lens. He finds that the sharp image forms 20 cm from the lens. (i) What is the approximate focal length of the lens? Explain. (ii) Find the power of the lens. (iii) Describe the nature and size of the image of the tree. (5 marks)
Read the passage and answer the questions. An optician has two lenses, A of power +4 D and B of power -2 D. A customer needs a lens that will form a real image of an object. (i) Find the focal length of each lens. (ii) Which lens can form a real image? Why? (iii) If an object is placed 50 cm from lens A, where will the image be formed? (5 marks)
Draw ray diagrams to show the image formed by a concave mirror when the object is placed (i) at infinity (ii) beyond C (iii) at C (iv) between F and C (v) at F (vi) between P and F. Prepare a table in words of position, size and nature of the image for each case, and state two uses of concave mirrors. (6 marks)
Explain, with a labelled diagram, the New Cartesian Sign Convention for spherical mirrors. Using it, solve: an object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and nature of the image formed. (6 marks)
Describe an activity to study refraction through a rectangular glass slab, drawing a labelled diagram. Show that the emergent ray is parallel to the incident ray, and explain lateral displacement. State the laws of refraction and define refractive index in terms of the speeds of light. (6 marks)
Draw ray diagrams for the image formed by a concave lens when the object is (i) at infinity (ii) between infinity and the optical centre. State the nature and size of the image in each case. A concave lens of focal length 15 cm forms an image 10 cm from the lens; find the object distance and magnification. (6 marks)
Define the power of a lens and its unit. Explain why the power of a convex lens is positive and that of a concave lens is negative. Find the power of a lens of focal length 25 cm and of -40 cm, and explain how opticians prescribe corrective lenses using power. Draw ray diagrams showing how a convex lens converges and a concave lens diverges a parallel beam. (6 marks)
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