Physics

Optics and Lenses

251 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

When the field behind a screen with an opening is added to the field of a complementary screen, the sum is equal to the field when there is no screen. Which of the following explains the above statement?

  1. Babinet’s principle

  2. Field equivalence principle

  3. Hansen–Woodyard principle

  4. None of these

  5. -
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When the field behind a screen with an opening is added to the field of a complementary screen, the sum is equal to the field when there is no screen.

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 can be corrected by a concave lens. It spreads the light out before it reaches the convex lens in the eye, thereby letting the image focus directly on the retina.

Multiple choice

Where should we place the object so as to get an enlarged, virtual and erect image using a convex lens?

  1. The object is placed beyond 2F.

  2. The object is placed at infinity.

  3. The object is placed at 2F.

  4. The object is placed between F and 2F.

  5. The object is placed between the pole (P) and F.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

When the object is placed between the pole (P) and F, the image will be formed on the same side of the object. The image will be virtual, erect and magnified.

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 evs magic with mirrors introduction to light and mirror image formation by plane mirror light : reflection and refraction from plane surface

A real image of a distant object is formed by a plano-convex lens on its principal axis. Spherical aberration

  1. is absent

  2. is smaller if the curved surface of the lens faces the object

  3. is smaller if the place surface of the lens faces the object

  4. is the same whichever side of the lens faces the object
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a plano-convex lens, spherical aberration is minimized when the curved surface faces the side with the smaller conjugate distance (the side with the more divergent rays). For a distant object, this means the curved surface should face the object.

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

The value of the focal length of the lens is equal to the value of the image distance when the rays are

  1. Passing through the optic centre

  2. Parallel to the principal axis

  3. Passing throught he focus

  4. Over the mirror
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When the object is placed at infinity, i.e., when the rays are parallel to the principal axis, the value of focal length is equal to the value of the image distance.

i.e., object distance , $u=\infty$
From lens formula,

$\dfrac 1f=\dfrac 1u+\dfrac 1v\\\implies \dfrac 1f=\dfrac 1\infty+\dfrac 1v\\\implies f=v$
i.e., image distance is equal to focal length of the lens.

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).