What is meant by power of a lens? Define the SI unit. You have two lenses A and B of focal lengths respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed from the lens? Draw ray diagrams to justify your answer.
Important Questions on Light : Reflection and Refraction
One half of a convex lens of focal length is covered with a black paper. Can such a lens produce an image of a complete object placed at a distance of from the lens? Draw a ray diagram to justify your answer.
A tall object is placed perpendicular to the principal axis of a convex lens of focal length . The distance of the object from the lens is . Find the nature, position and size of the image.
Analyse the following observations table showing variation of image distance () with object distance () in case of a convex lens and answer the questions that follow, without doing any calculations:
| S.No. | Object distance u(cm) |
Image distance v(cm) |
(a) What is the focal length of the convex lens? Give reason in support of your answer.
(b) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(c) Take an appropriate scale to draw ray diagram for the observation at S.No. and find the approximate value of magnification.
Which of the following can make a parallel beam of light when light from a point source is incident on it?
A long awl pin is placed vertically in front of a concave mirror. A long image of the awl pin is formed at in front of the mirror. The focal length of this mirror is
Under which of the following conditions a concave mirror can form a real image larger than the actual object?
A light ray enters from medium A to medium B as shown in the figure. The refractive index of medium A relative to B will be
Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in figure. Which of the following could be inside the box?
