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प्रश्न
पर्याय
40 cm
25 cm
`1/40` cm.
`1/25` cm
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उत्तर
The power of a convex lens is 2.5 dioptres. Its focal length is 40 cm.
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संबंधित प्रश्न
"A convex lens can form a magnified erect as well as magnified inverted image of an object placed in front of it." Draw ray diagram to justify this statement stating the position of the object with respect to the lens in each case.
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.
Draw a ray diagram to show the formation of the image of an object be placed so that a real and inverted image of the same size as the object is obtained using a convex lens
If the image formed by a convex lens is of the same size as that of the object, what is the position of the image with respect to the lens?
Where should an object be placed in order to use a convex lens as a magnifying glass?
You eye contains a convex lens. Why is it unwise to look at the sun?
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 of focal length 6 cm is held 4 cm from a newspaper which has print 0.5 cm high. By calculation, determine the size and nature of the image produced.
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.
- Rewrite the image distances in the correct order.
- What would be the image distance if the object distance was 90 cm?
- Which of the object distances gives the biggest image?
- What is the focal length of this lens?
Complete the following sentence.
A long-sighted person cannot see ........... objects clearly. Long-sightedness can be corrected by using .............. lenses.
In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?
For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.
What is the difference between a double convex and a bi-convex lens?
State the position of object, position of image, nature of image when: Convex lens is used as in searchlight.
: Object near the lens : : ______ : 
Write the name.
The lens used in simple microscope.
Which of the following statements is true?
