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JEE Advanced Ray Optics and Optical Instruments — practice questions — page 3

Explore 88 free Ray Optics and Optical Instruments questions in JEE Advanced Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Ray Optics and Optical Instruments questions and exercises with answers

Showing questions 61–88 of 88.

Converging or diverging?Read the answer and worked solution →Two plane mirrors are inclined at an angle of $60^\circ$. The number of images of a point object placed between them is:Read the answer and worked solution →An object is placed $30\,\text{cm}$ in front of a concave mirror of focal length $20\,\text{cm}$. The image distance from the mirror is:Read the answer and worked solution →True or false: optical fibresRead the answer and worked solution →Reading the laws backRead the answer and worked solution →The power P of a lens of focal length f (in metres) is given byRead the answer and worked solution →Refractive index of water with respect to air is 4/3. The critical angle for a water–air interface is approximatelyRead the answer and worked solution →Light passes from air (n=1) into glass (n=1.5) at an incidence angle of 60°. Using Snell's law, the angle of refraction isRead the answer and worked solution →For a thin prism of small refracting angle A and refractive index n, the deviation δ is approximatelyRead the answer and worked solution →The apparent depth of an object lying at the bottom of a pool of water (n = 4/3) is, in terms of its real depth h,Read the answer and worked solution →A thin prism of refracting angle 5° is made of glass with n = 1.5. The deviation δ of a light ray passing through it is approximatelyRead the answer and worked solution →Two thin convex lenses, each of focal length 20 cm, are placed coaxially 10 cm apart in air. The equivalent focal length of the combination isRead the answer and worked solution →Cartesian sign convention: positive or negative?Read the answer and worked solution →Critical angleRead the answer and worked solution →Lenses in contactRead the answer and worked solution →Order the steps: solve a mirror problemRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →True or false: optical instrumentsRead the answer and worked solution →Which instrument does this belong to?Read the answer and worked solution →A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 25 cm. The power of the combination (in dioptres) isRead the answer and worked solution →Complete the prism relationRead the answer and worked solution →An astronomical telescope in normal adjustment has an objective of focal length 100 cm and an eyepiece of focal length 5 cm. Its angular magnification isRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Which quantity is being described?Read the answer and worked solution →Tap every example of total internal reflectionRead the answer and worked solution →Match each formula to what it describesRead the answer and worked solution →A point source of light is placed at the origin in an isotropic medium. The wavefronts associated with the light are:Read the answer and worked solution →The mirror equation relates u, v and f asRead the answer and worked solution →

Worked practice questions

Converging or diverging?

Read exercise and reference answers
Items
  1. Item
    Focal length is positive
    Category
    Converging
  2. Item
    Power is positive
    Category
    Converging
  3. Item
    A convex lens
    Category
    Converging
  4. Item
    Focal length is negative
    Category
    Diverging
  5. Item
    Power is negative
    Category
    Diverging
  6. Item
    A concave lens
    Category
    Diverging
Categories
  1. Item
    Converging
  2. Item
    Diverging
A positive focal length converges, a negative one diverges, and power carries the same sign as f. Source: syllabus Physics Part II, Ch 9 Ray Optics and Optical Instruments.

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Two plane mirrors are inclined at an angle of $60^\circ$. The number of images of a point object placed between them is:

  1. $3$
  2. $4$
  3. $5$
  4. $6$
Show answer and solution

Correct answer: C. $5$

When $360^\circ/\theta$ is an integer, the number of images is $n = \dfrac{360^\circ}{\theta} - 1$. Here $360^\circ/60^\circ = 6$, an integer, so $n = 6 - 1 = 5$.

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An object is placed $30\,\text{cm}$ in front of a concave mirror of focal length $20\,\text{cm}$. The image distance from the mirror is:

  1. $+12\,\text{cm}$
  2. $-60\,\text{cm}$
  3. $+60\,\text{cm}$
  4. $-12\,\text{cm}$
Show answer and solution

Correct answer: B. $-60\,\text{cm}$

Using the standard sign convention, $u = -30\,\text{cm}$ and $f = -20\,\text{cm}$ for a concave mirror. The mirror formula $\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$ gives $\dfrac{1}{v} = \dfrac{1}{-20} - \dfrac{1}{-30} = -\dfrac{1}{60}$, so $v = -60\,\text{cm}$. The negative sign indicates the image is real and on the same side as the object, $60\,\text{cm}$ in front of the mirror.

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