Myopia, or short-sightedness, is corrected by using which type of lens?
- A.Convex lens
- B.Concave lens
- C.Cylindrical lens
- D.Bifocal lens
Correct answer
Explanation
The correct answer is B, a concave lens. In myopia the eyeball is too long or the lens of the eye too strongly converging, so rays from a distant object meet in front of the retina and the person cannot see far objects clearly. A concave lens diverges the incoming rays before they enter the eye, so the image is pushed back and falls exactly on the retina.
Option A, a convex lens, converges light and is used for hypermetropia or long sight, where the image forms behind the retina and near objects look blurred. Option C, a cylindrical lens, corrects astigmatism, which is caused by an uneven curvature of the cornea. Option D, a bifocal lens, has a concave upper part and a convex lower part and is used for presbyopia, the loss of the power of accommodation with age.
Read the full article: Light: Reflection and Refraction Notes with PYQs
Practice Questions
View allA ray of light travelling from a rarer medium to a denser medium:
- A.slows down and bends away from the normal
- B.slows down and bends towards the normal
- C.speeds up and bends away from the normal
- D.speeds up and bends towards the normal
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A denser medium has a higher refractive index, and the refractive index is the speed of light in vacuum divided by its speed in the medium, so light must travel more slowly inside it.
Read the full explanation →A concave lens has a focal length of 15 cm. If the object is placed at 30 cm from the lens, what is the image distance?
- A.-20 cm
- B.-10 cm
- C.-15 cm
- D.-18 cm
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By the sign convention the focal length of a concave lens is negative, so f is minus 15 centimetres, and the object distance measured against the direction of the incident light is minus 30 centimetres.
Read the full explanation →Name the scientist who first used a glass prism to obtain the spectrum of sunlight.
- A.C. V. Raman
- B.Lord Rayleigh
- C.Isaac Newton
- D.S. Chandrasekhar
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Newton passed a narrow beam of sunlight through a glass prism in a darkened room and obtained a band of seven colours on the wall, which he named the spectrum.
Read the full explanation →The image formed by a plane mirror is always:
- A.Real, inverted and of the same size
- B.Virtual, erect and of the same size
- C.Virtual, erect and diminished
- D.Real, erect and magnified
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Rays reflected from a plane mirror diverge and only appear to come from a point behind the mirror, so the image cannot be caught on a screen and is virtual.
Read the full explanation →Which type of mirror is used as a rear-view mirror in vehicles?
- A.Plane mirror
- B.Concave mirror
- C.Convex mirror
- D.Cylindrical mirror
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A convex mirror curves outward and spreads the light that falls on it, so it always forms a virtual, erect and diminished image, whatever the distance of the object.
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