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प्रश्न
Choose the correct alternative and rewrite the following:
Inside water, an air bubble behaves ....................
विकल्प
always like a flat plate
always like a concave lens
always like a convex lens
always like a concave mirror
उत्तर
always like a concave lens
- Inside water, the air bubble behaves like a Concave lens. The concave lenses are known as diverging lenses as the rays diverge after falling on the concave lens.
- The concave lens diverges a straight light beam coming from the source to a diminished, upright, virtual image and forms both real and virtual images.
- The air bubble is a sphere with a convex surface and when light reaches it, the light is reflected within the water as in a concave lens.
The refractive index of air = 1 and
The index of water = 1.33.
Since the water refractive index is greater than air, the air bubbles in the water will behave like a concave lens.
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संबंधित प्रश्न
Where must the object be placed for the image formed by a converging lens to be:
real, inverted and smaller than the object?
Where must the object be placed for the image formed by a converging lens to be:
real, inverted and larger than the object?
Draw a diagram to show how a converging lens focusses parallel rays of light?
If the image formed by a lens is always diminished and erect, what is the nature of the lens?
Which type of lenses are:
thinner in the middle than at the edges?
Fill in the following blank with suitable word:
Lenses refract light to form images: a..................... lens can form both real and virtual images, but a diverging lens forms only ...................... images.
Which type of lens is :
a converging lens, and which is
An object is placed 10 cm from a lens of focal length 5 cm. Draw the ray diagrams to show the formation of image if the lens is diverging.
State one practical use each of convex mirror, concave mirror, convex lens and concave lens.
When sunlight is concentrated on a piece of paper by a spherical mirror or lens, then a hole can be burnt in it. For doing this, the paper must be placed at he focus of:
(a) either a convex mirror or convex lens
(b) either a concave mirror or concave lens
(c) either a concave mirror or convex lens
(d) either a convex mirror or concave lens
A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
The power of a concave lens is 10 D and that of a convex lens is 6 D. When these two lenses are placed in contact with each other, the power of their combination will be :
(a) +16 D
(b) +4 D
(c) −16 D
(d) −4 D
The power of a lens is negative. State whether it is convex or concave.
An object is placed at a distance 24 cm in front of a convex lens of focal length 8 cm.
(i) What is the nature of the image so formed?
(ii) Calculate the distance of the image from the lens.
(iii) Calculate the magnification of the image.
When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. This image is :
Define the principal focus of a concave lens.
Define the term principal foci as applied to a concave lens. Illustrate your answer with the aid of proper diagrams. Show the focal length of the lens in the diagram.
Draw images in case of a concave lens when the object is at infinity.
Draw images in case of a concave lens when the object is at any point on the principal axis between the lens and infinity.
