Advertisements
Advertisements
प्रश्न
Find the focal length of a lens of power −2.0 D. What type of lens is this?
Advertisements
उत्तर
Power of lens,
P = −2.0 D
P = `1/"f"`
∴ f = `1/"P"`
= `1/(-2.0 "D")`
= −0.5 m
A concave lens has a negative focal length. Hence, it is a concave lens.
APPEARS IN
संबंधित प्रश्न
Find the power of a concave lens of focal length 2m.
(a) At what distance should the lens be held from the figure in order to view the squares distinctly with the maximum possible magnifying power?
(b) What is the magnification in this case?
(c) Is the magnification equal to the magnifying power in this case? Explain.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
Consider two statements A and B given below:
A: real image is always inverted
B: virtual image is always erect
Out of these two statements:
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
What is the power of a convex lens of focal length 0.5 m?
A diverging lens has focal length of 3 cm. Calculate the power.
The power of a lens is, −2 D. What is its focal length?
The focal length of a lens is +150 mm. What kind of lens is it and what is its power?
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
What is the unit of power of a lens? Define the unit of power of a lens.
A combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.A optical instrument in which the above arrangement of convex lens is used is a convex lens used to burn paper by focusing sunlight.
How does the power of a lens change if its focal length is doubled?
A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be
According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth power of its ______.
Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accommodation |
The above lens has a focal length of 10 cm. The object of height 2 mm is placed at a distance of 5 cm from the pole. Find the height of the image.
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
