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
What does sign of power (+ve or –ve) indicate?
Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct? Give a reason for your answer.
Kavita from 10th is using spectacles. The power of the lenses in her spectacles is –2.5 dioptre. Answer the following questions:
1) Which lenses are used in her spectacles?
2) State the defect of vision Kavita is suffering from.
3) Find the focal length of the lenses used in her spectacles
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
Name the physical quantity whose unit is dioptre.
What is the power of a convex lens lens whose focal length is 80 cm?
What is the nature of a lens whose power is, −4 D?
The power of a combination of two lenses X and Y is 5 D. If the focal length of lens X be 15 cm :
(a) calculate the focal length of lens Y.
(b) state the nature of lens Y.
What is the unit of power of a lens? Define the unit of power of a lens.
A converging lens has a focal length of 50 cm. The power of this lens is:
A diverging lens has a focal length of 0.10 m. The power of this lens will be:
Express the power (with sign) of a concave lens of focal length 20 cm.
A symmetric double convex lens is cut in two equal parts by a plane containing the principal axis. If the power of the original lens was 4 D, the power of a divided lens will be
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
The power of the magnifying glass depends on the distance of the magnifying glass from object.
Power of a lens is – 4D, then its focal length is
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 |
A convex lens with radii of curvature R1 = R2 is immersed in water. Assuming that the refractive indices of glass and water are 3/2 and 4/3 respectively, its focal length f1 in comparison to that in air, f, is ______.
An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is
- negative and
- positive.
The power of convex lens of focal length 20 cm is ______.
