Advertisements
Advertisements
प्रश्न
The power of convex lens of focal length 20 cm is ______.
विकल्प
+5.0 D
0.20 D
-5.0 D
0.5 D
Advertisements
उत्तर
The power of convex lens of focal length 20 cm is +5.0 D.
Explanation:
Given: Focal length = f = 20 cm = 0.2 m
Power of the lens = P = ?
P = `1/("f"("m"))`
= `1/0.2`
= 5 D
The power of the lens is 5 D.
APPEARS IN
संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2D.
Calculate the focal length of a corrective lens having power +2.5 D.
Define the power of a lens.
What does sign of power (+ve or –ve) indicate?
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
Find the focal length of a lens of power −2.0 D. What type of lens is this?
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
Name the physical quantity whose unit is dioptre.
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
How is the power of a lens related to its focal length?
Which has more power : a thick convex lens or a thin convex lens, made of the same glass? Give reason for your choice.
What is the power of a convex lens of focal length 0.5 m?
What is the power of a convex lens lens whose focal length is 80 cm?
The power of a lens is, −2 D. What is its focal length?
An object of height 4 cm is placed at a distance of 15 cm in front of a concave lens of power, −10 dioptres. Find the size of the image.
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with one another.
(a) What is the power of this combination?
(b) What is the focal length of this combination?
(c) Is this combination converging or diverging?
What do you understand by the power of a lens?
State the condition for the following a lens has both its focal lengths equal .
State the condition for the following a ray passes undeviated through the lens .
How is the power of a lens related to its focal length?
On reducing the focal length of a lens, its power ______.
The power of a lens is + 1.0 D is :
Express the power (with sign) of a concave lens of focal length 20 cm.
Define power of a lens. Write its units. Deduce the relation `1/f =1/f_1 +1/f_2`for two thin lenses kept in contact coaxially.
Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.
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
Consider three converging lenses L1, L2 and L3 having identical geometrical construction. The index of refraction of L1 and L2 are \[\mu_1 \text{ and } \mu_2\] respectively. The upper half of the lens L3 has a refractive index \[\mu_1\] and the lower half has \[\mu_2\] following figure . A point object O is imaged at O1 by the lens L1 and at O2 by the lens L2placed in same position. If L3 is placed at the same place,
(a) there will be an image at O1
(b) there will be an image at O2.
(c) the only image will form somewhere between O1 and O2
(d) the only image will form away from O2.
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
The power of a lens is +2.0 D. Find its focal length and state the kind of lens.
A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above.
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.
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 focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?
