Advertisements
Advertisements
प्रश्न
Write scientific reason.
Adults need bifocal lens spectacle.
Advertisements
उत्तर
- The ability of the ciliary muscles near the eye lens to change the focal length of the lens decreases with age.
- As a result, sometimes adults suffer from both nearsightedness and farsightedness.
Therefore, adults need bifocal lens spectacle.
APPEARS IN
संबंधित प्रश्न
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
"A lens can form a magnified erect image as well as magnified inverted image of an object placed in front of it." State the nature of this lens and draw ray diagrams to justify the above statement. Mark the positions of O, F and 2F in the diagram.
Distinguish between a convex lens and concave lens. Which of the two is a converging lens : convex lens of concave lens?
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.
A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.
A convex lens of focal length 0.10 m is used to form a magnified image of an object of height 5 mm placed at a distance of 0.08 m from the lens. Calculate the position, nature and size of the image.
Which of the above two cases illustrates the working of a magnifying glass?
A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.
What is the focal length of this lens?
What kind of lens can form:
an erect magnified image?
What kind of lens is used to correct
long-sightedness?
A convex lens is placed in water. Its focal length will ______.
In the following cases, where must an object be placed in front of a convex lens so that the image formed is upright and enlarged?
State two applications of a convex lens.
Point out the difference between a convex lens and a concave lens.
How will you determine the focal length of a convex lens by the plane mirror method?
A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object be placed in each case for obtaining these images?
- In which type of microscope do you find the lens arrangement as shown in the following diagram?
- Write about the working and the use of this microscope.
Distinguish between Concave lens and Convex lens.
Distinguish between:
Concave lens and Convex Lens
