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 physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

Sunlight of intensity 1.3 kW m–2 is incident normally on a thin convex lens of focal length 20 cm. Ignore the energy loss of light due to the lens and assume that the lens aperture size is much smaller than its focal length. The average intensity of light, kW m–2, at a distance 22 cm from the lens on the other side is _________. 

  1. $ 130 $
  2. $120 \ $
  3. $ 170$
  4. $160 $
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

A thin plano-convex lens acts like concave mirror of focal length $0.2m$ when silvered at its plane surface. Refractive index of the material of lens is $1.5$. Radius of curvature of convex surface of the lens is

  1. $0.1m$
  2. $0.2m$
  3. $0.4m$
  4. $0.8m$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a silvered plano-convex lens, the focal length is given by 1/f = 2/f_lens + 1/f_mirror. With f_mirror = infinity (plane surface) and f_lens = R/(n-1), the effective focal length is R/(2(n-1)). Setting this to 0.2m with n=1.5 yields R = 0.2m.

Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

A plane-convex lens has a refractive index of 1.6 and a radius of curvature 60 cm. What is the focal length of the lens? 

  1. 50 cm

  2. 100 cm

  3. 200 cm

  4. 150 cm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

${R _1} = 60\,cm,\,\,{R _2} = \infty ,\,\,\mu  = 1.6$

$\frac{1}{f} = \left( {\mu  - 1} \right)\left( {\frac{1}{{{R _1}}} - \frac{1}{{{R _2}}}} \right)$
$\frac{1}{f} = \left( {1.6 - 1} \right)\left( {\frac{1}{{60}}} \right)$
$ = f = 100\,cm.$
Hence,
option $(B)$ is correct answer.

Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

Which statement is correct for a zone plate and a lens?

  1. Zone plate has multi focii whereas lens has one

  2. Zone plate has one focus whereas lens has multiple focii

  3. Both are correct

  4. Zone plane has one focus whereas a lens has infinite
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A zone plate acts like a lens with multiple foci because it is based on diffraction zones, whereas a standard refractive lens has a single focal point determined by its geometry and refractive index.

Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

A point on the principal axis of a lens, to which light rays parallel to the principal axis converge after passing through the lens, is ............

  1. Centre of curvature

  2. Origin

  3. Focus

  4. Optical centre
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A point on the principal axis of a lens, to which light rays parallel to the principal axis converge after passing through the lens, is  called focus of the lens.


Answer-(C).

Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

For which of the following is $f > 0$:

I. Concave mirror
II. Convex mirror
III. Converging lens
 

  1. I only

  2. II only

  3. I and III only

  4. II and III only

  5. I, II, and III
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In this style of multiple-choice question, the I, II, and III questions provide you with three possible answers, and the five answer choices list different combinations of those three. Theres an upside and a downside to questions like these. Suppose you know that a concave mirror has f >0 and a convex mirror doesnt, but youre not sure about a converging lens. The downside is that you cant get the right answer for sure. The upside is that you can eliminate B, D, and E, and have a 50% chance of guessing the right answer. As long as youre not afraid to guessand you should never be afraid to guess if youve eliminated an answerthese questions shouldnt be daunting. 
The value of f for a converging lens is positive, so the answer is C . 

Multiple choice physics lens technical terms related to lens terms related to lenses introduction to lenses and its types

A convex and a concave lens separated by distance $d$ are then put in contact. The focal length of the combination

  1. Decreases

  2. Increases
  3. Becomes $0$

  4. Remains the same
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\dfrac{1}{f _r}=\dfrac{1}{f _1}+\dfrac{1}{f _2}-\dfrac{d}{f _1f _2}$

So when are brought in contact $d=0$, hence focal length $f _r$ will decrease .

Multiple choice perceive colours resolution of optical instruments lenses option c: imaging physics

The focal length of a thin convex lens for red and blue rays are $100\ cm$ and $96.8\ cm$ respectively. The dispersive power of the material of the lens is

  1. 0.0325

  2. 0.825

  3. 0.968

  4. 0.98
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dispersive power (omega) for a thin lens is (f_r - f_b) / f_mean. f_mean = (100 + 96.8) / 2 = 98.4. Omega = (100 - 96.8) / 98.4 = 3.2 / 98.4 = 0.0325.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

If you want to make Refracting Telescope, what components will you choose ?

  1. One convex led and one concave lens.

  2. Two convex lenses.

  3. One concave mirror, one plane mirror and one convex lens.

  4. Once concave mirror, one convex mirror and one convex lens.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A refracting telescope uses two convex lenses: an objective lens to gather light and an eyepiece lens to magnify the image.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

Match the items given in A, B, C and D against their corresponding description given in 1, 2, 3, 4 and 5.
A. Astronomical telescope
B. Galilean Telescope
C. Simple Microscope
D. Compound Microscope

1. Contains one convex lens
2. Contains one concave lens
3. Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece
4. Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
5. Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece. 

  1. $2\, \quad\, 3\, \quad\, 1\, \quad\, 5$
  2. $3\, \quad\, 2\, \quad\, 4\, \quad\, 1$
  3. $2\, \quad\, 5\, \quad\, 3\, \quad\, 4$
  4. $3\, \quad\, 5\, \quad\, 1\, \quad\, 4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A). Astronomical telescope - Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece

B.) Galilean Telescope - Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece
C). Simple Microscope - Contains one convex lens
D.) Compound Microscope - Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
Thus,
A  -  3 , B  -  5 , C  -  1 and D  -  4 , hence Option D is correct.

Multiple choice newton's colour disc light and the formation of shadows physics

When a drop of water is introduced between the glass plate and plano-convex lens in Newton's rings system, the ring system

  1. Contracts

  2. Expands

  3. Remains same

  4. First expands then contracts
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The diameter of Newton's rings is inversely proportional to refractive index. Therefore when a drop of water is introduced between the glass plate and plano-convex lens in Newton's rings, the ring system contacts. 

Multiple choice newton's colour disc light and the formation of shadows physics

In the Newton's rings set up, when a drop of water is introduced between the glass plate and planoconvex lens the observed ring system

  1. Contracts

  2. Expands

  3. Remains the same

  4. Expands and then contracts
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since diameter of the ring is inversely proportional to the square root of refractive index of the medium between the planoconvex lens and plane glass plate, therefore as refractive index increases, diameter of the rings decrease, that is the rings contract.