Advertisements
Advertisements
प्रश्न
The optician's prescription for a spectacle lens is marked +0.5 D. What is the:
(a) nature of spectacle lens?
(b) focal length of spectacle lens?
Advertisements
उत्तर
Positive power indicates it is a converging lens.
Power of a lens is given by:
power(p)=`1/f`
`0.5=1/f`
`f=1/0.5`
`f=2m`
APPEARS IN
संबंधित प्रश्न
What is meant by a power of a lens? Define its SI unit.
Define the power of a lens.
(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.
A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each 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:
The lens A has a focal length of 25 cm whereas another lens B has a focal length of 60 cm. Giving reason state, which lens has more power: A or B.
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
What is the nature of a lens whose power is, −4 D?
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 do you understand by the power of a lens? Name one factor on which the power of a lens depends.
The power of a lens is +2.0D. Its focal length should be :
Define the term focal length of a lens.
How is the sign (+ or -) of power of a lens related to its divergent or convergent action?
Express the power (with sign) of a concave lens of focal length 20 cm.
A double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
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
A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
According to Rayleigh’s scattering law, the amount of scattering of light is inversely proportional to the fourth power of its ______.
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.
