Physics

Optics and Lenses

206 Questions

Enhance your physics knowledge by practicing questions on optics and the functioning of lenses. The set covers calculating combined focal lengths, lens power, and correcting vision defects like myopia and hypermetropia. These physics fundamentals are crucial for medical entrance and state board exams.

Combined focal lengthCorrecting vision defectsLens power calculationConvex and concave lensesTelescopesHuygens principle

Optics and Lenses Questions

Multiple choice general knowledge

Short-sightedness can be corrected by using

  1. Convex-concave lens

  2. Concave-convex lens

  3. Convex lens

  4. Concave lens
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Short-sightedness (myopia) occurs when the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina. A concave lens diverges light before it enters the eye, moving the focal point back onto the retina. Convex lenses would worsen the condition.

Multiple choice general knowledge science & technology

What is the name of the point where light rays from infinity coverge after passing through a lens?

  1. Center

  2. Infinity

  3. Parabola

  4. Focus
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The focus is the point where parallel light rays (from infinity) converge after passing through a lens. This is a fundamental principle in geometric optics. The center is the middle of the lens, infinity is a theoretical distance, and parabola is a type of curve.

Multiple choice

A Converging lens of power 4 D is kept in contact with a diverging lens of power - 2 D. The nature and the focal length of the combination is-

  1. Converging 25 cm

  2. Converging 50 cm

  3. Diverging 25 cm

  4. Diverging 50 cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The combined power is 4 D + (-2 D) = 2 D (positive, so converging). Focal length = 1/Power = 1/2 = 0.5 m = 50 cm. A positive power means converging lens. The diopter (D) unit is the reciprocal of focal length in meters.

Multiple choice

Which type of lens is used for correcting astigmatism?

  1. Concave lens

  2. Convex lens

  3. Plane lens

  4. Cylindrical lens

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Astigmatism is caused by an irregular curvature of the cornea or lens, making vision distorted at all distances. Cylindrical lenses have different curvatures in different directions and can correct this irregularity. Concave and convex lenses have uniform curvature, while 'plane lens' is not a standard optical term.

Multiple choice

A hypermetropic person may use _____.

  1. a concave lens

  2. a convex lens

  3. a plano convex lens

  4. a plano concave lens
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hypermetropia (farsightedness) occurs when the eye is too weak or too short, focusing images behind the retina. A convex (converging) lens adds focusing power to bring images forward onto the retina. Concave lenses are for myopia, while plano-convex and plano-concave describe lens shapes, not the complete solution.

Multiple choice

A double convex glass lens of focal length f and having a circular aperture is cut into two halves, each having a semicircular aperture. The focal length of each half is

  1. f

  2. 2f

  3. f/2

  4. Infinity
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When a convex lens is cut into two halves along the principal axis, each half maintains the same curvature of surfaces as the original lens. Since focal length depends on the radii of curvature of the lens surfaces and the refractive index, and these properties remain unchanged, the focal length of each half remains the same as the original lens (f). The aperture size reduces but does not affect focal length.

Multiple choice

Short-sightedness can be corrected by

  1. concave-convex lens

  2. concave lens

  3. convex lens

  4. convex-concave lens
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Short-sightedness (myopia) occurs when the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina. A concave lens diverges light before it enters the eye, moving the focal point back onto the retina and correcting the vision defect.