Advertisements
Advertisements
प्रश्न
For a specific glass lens f = 0.5 m. This is the only information given to the student. Which type of lens is given to him and what is its power?
पर्याय
power 2 D; convex lens
power 1 D; concave lens
power - 0.5 D; concave lens
power - 0.25 D; convex lens
Advertisements
उत्तर
power 2 D; convex lens
APPEARS IN
संबंधित प्रश्न
A student focuses the image of a well-illuminated distant object on a screen using a convex lens. After that, he gradually moves the object towards the lens and each time focuses its image on the screen by adjusting the lens.
(i) In which direction, towards the screen or away from the screen, does he move the lens?
(ii) What happens to the size of the image? Does it decrease or increase?
(iii) What happens to the image on the screen when he moves the object very close to the lens?
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
Draw a labelled ray diagram to show how a ray of light is refracted when it passes:
from an optically denser medium into air.
With the help of a labelled diagram explain how a convex lens converges a beam of parallel light rays. Mark the principal axis, optical centre, principal focus and focal length of the convex lens on the diagram.
In order to obtain a real image twice the size of the object with a convex lens of focal length 15 cm, the object distance should be:
(a) more than 5 cm but less than 10 cm
(b) more than 10 cm but less than 15 cm
(c) more than 15 cm but less than 30 cm
(d) more than 30 cm but less than 60 cm
What type of images can a convex lens make?
What would be the diameter of the image of the flower on the film?
An image formed on a screen is three times the size of the object. The object and screen are 80 cm apart when the image is sharply focussed.
State which type of lens is used.
The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having greatest power is :
(a) P
(b) Q
(c) R
(d) S
Show by a diagram the refraction of two light rays incident parallel to the principal axis on a convex lens by treating it as a combination of a glass slab and two triangular glass prisms.
Study the diagram below.
what are the points O, O’ called?
A lens forms an inverted image of an object. Name the kind of lens.
In the following cases, where must an object be placed in front of a convex lens so that the image formed is of the same size as the object?
Complete the following table:
| Type of lens | Position of object | Nature of image | Size of image |
| Convex | Between optical centre and focus | ||
| Convex | At focus | ||
| Concave | At infinity | ||
| Concave | At any distance |
A student places a 8.0 cm tall object perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. He obtains a sharp image of the object on a screen placed on the other side of the lens. What will be the nature (inverted, erect, magnified, diminished) of the image he obtains on a screen? Draw ray diagram to justify your answer.
i. Which type of microscope has the arrangement of lenses shown in the adjoining figure?
ii. Label the figure correctly.
iii. Write the working of this microscope.
iv. Where does this microscope used?
v. Suggest a way to increase the efficiency of this microscope.
Answer the following question.
List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining an image of a distant object on a screen.
State the position of object, position of image, nature of image when: Convex lens is used as in searchlight.
Diagram shows an object AB placed on the principal axis B of a convex lens placed in air. F1 and F2 are the two foci of the lens.
(i) Copy the diagram:
Draw a ray of light starting from B and passing through O. Show the same ray after refraction by the lens. Draw another ray from B which passes through F2 after refraction by the lens. Locate the final image
(ii) Is the image real or virtual?
Find the odd one out and give its explanation.
