Advertisements
Advertisements
Question
Which of the following statements is true?
Options
A convex lens has 4 dioptre power having a focal length 0.25 m
A convex lens has –4 dioptre power having a focal length 0.25 m
A concave lens has 4 dioptre power having a focal length 0.25 m
A concave lens has –4 dioptre power having a focal length 0.25 m
Solution
A convex lens has 4 dioptre power having a focal length 0.25 m
Explanation -
The focal length and the power of concave lens is always negative and of convex lens is positive. The relation between power and focal length is, `"P" = 1/"f"`
Using this formula to find power,
`"P" = 1/"f"`
`= 1/0.25`
= 4D
APPEARS IN
RELATED QUESTIONS
An object is placed at a distance equal to 2f in front of a convex lens. Draw a labelled ray diagram to show the formation of image. State two characteristics of the image formed.
What type of lens is shown in the diagram on the right? What will happen to the parallel rays of light? Show by completing the ray diagram.
Name one simple optical instrument in which the above arrangement of convex lens is used.
A convex lens of focal length 8 cm forms a real image of the same size as the object. The distance between object and its image will be:
(a) 8 cm
(b) 16 cm
(c) 24 cm
(d) 32 cm
What kind of lens can form:
an inverted diminished image?
A camera fitted with a lens of focal length 50 mm is being used to photograph a flower that is 5 cm in diameter. The flower is placed 20 cm in front of the camera lens.
At what distance from the film should the lens be adjusted to obtain a sharp image of the flower?
A convex lens has a divergent action and a concave lens has a convergent action.
State the position of object, position of image, nature of image when: Convex lens is used as an erecting lens in terrestrial telescope.
A concave mirror and convex lens are held in water. What changes, if any, do you expect in their focal length?
Distinguish between:
Concave lens and Convex Lens
