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प्रश्न
When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.
What is the focal length of lens B?
उत्तर
The focal length of lens B is 5 cm as only a converging lens forms a real, inverted and same size image of object when the object is placed at 2F position of the lens.
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संबंधित प्रश्न
Which type of lenses are:
thinner in the middle than at the edges?
Give the position, size and nature of image of formed by a concave lens when the object is placed:
at infinity.
With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.
When an object is kept at any distance in front of a concave lens, the image formed is always:
(a) virtual, erect and magnified
(b) virtual, inverted and diminished.
(c) virtual, erect and diminished
(d) virtual, erect and same size as object
A beam of light is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the following figure:
The box contains:
(a) a glass prism
(b) a concave lens
(c) a convex lens
(d) a parallel-sided glass slab
(a) Find the position and size of the virtual image formed when an object 2 cm tall is placed 20 cm from:
(i) a diverging lens of focal length 40 cm.
(ii) a converging lens of focal length 40 cm.
(b) Draw labelled ray diagrams to show the formation of images in case (i) and (ii) above (The diagrams may not be according to scale).
What type of lens is used to correct
myopia?
Study the diagram below.
- Name the lens LL’.
- What are the points O and O' called ?
- Complete the diagram to form the image of the object AB.
- State three characteristics of the image.
Where will the image be formed if an object is kept in front of a concave lens at a distance equal to its focal length? Draw a ray diagram to illustrate your answer.
An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm.
(i) Use the lens formula to find the distance of the image from the lens.
(ii) List four characteristics of the image (nature, position, size, erect/inverted) formed by the lens in this case.
(iii) Draw a ray diagram to justify your answer of the part (ii).
