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प्रश्न
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?
उत्तर
(a) If the victim's spectacles are fitted with convex lens, the detective can conclude that the victim was long-sighted. A person suffering from long-sightedness, or hypermetropia, wears spectacles with convex lenses to correct the defect.
(b) If the victim's spectacles are fitted with concave lens, the detective can conclude that the victim was short-sighted. A person with short-sightedness, or myopia, wears spectacles with concave lenses to correct the defect.
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संबंधित प्रश्न
When a ray of light enters from one medium to another having different optical densities it bends. Why does this phenomenon occur?
An object of height 4.0 cm is placed at a distance of 30 cm from the optical centre 'O' of a convex lens of focal length 20 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre 'O' and principal focus 'F' on the diagram. Also find the approximate ratio of size of the image to the size of the object.
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 would be the image distance if the object distance was 90 cm?
Which part causes the greatest convergence?
Define the term principal axis of a lens.
A convex lens forms an image of an object equal to the size of the object. State two more characteristics of the image.
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 happens to the image formed by a convex lens if its lower part is blackened?
Distinguish between:
Concave lens and Convex lens
