Advertisements
Advertisements
Question
A 50 cm tall object is at a very large distance from a diverging lens. A virtual, erect and diminished image of the object is formed at a distance of 20 cm in front of the lens. How much is the focal length of the lens?
Advertisements
Solution
Since the object is at infinity, the image will be formed at the focus. The image distance will be equal to the focal length of the lens. Therefore, the focal length of the lens is 20 cm.
APPEARS IN
RELATED QUESTIONS
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. A 4 cm tall object is placed perpendicular to its 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.
An image that cannot be obtained on a screen is called ______.
An image formed by a ______ mirror is always of the same size as that of the object.
Name the two types of spherical mirrors. What type of mirror is represented by the:
front side of a shining steel spoon?
State the two convenient rays that are chosen to construct the image by a spherical mirror for a given object? Explain your answer with the help of suitable ray diagrams.
State the position of object for which the image formed by a concave mirror is of same size.
Write two more characteristics of the image.
How is the focal length of a spherical mirror related to its radius of curvature?
What is meant by magnification? Write its expression. What is its sign for the (a) real (b) virtual, image?
A concave mirror forms a virtual image of size twice that of the object placed at a distance 5 cm from it. Find:
- the focal length of the mirror
- position of image
Define the following term in relation to concave mirror.
Center of curvature
Define the following term in relation to concave mirror.
Principal axis
Define the term principal focus in case of convex mirror. Draw a convex mirror and show its principal focus and focal length clearly.
What is the relationship between the focal length and radius of curvature?
Define the term Normal.
Numerical problem.
The radius of curvature of a spherical mirror is 25 cm. Find its focal length.
If the real image of a candle flame formed by a lens is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens?
Name the two types of spherical mirrors.
