12 questions

Class 10 Light: Refraction, Lenses and Refractive Index

Class 10 · why light bends, Snell's law and refractive index, images in convex and concave lenses with ray diagrams to read, and the glass slab. CBSE Chapter 9, part 2.

Questions

12 questions in this version · Correct answers are hidden so you can test yourself first.

  1. 1Question 1

    A pencil standing in a glass of water looks bent at the water surface. What causes this?

    AReflection of light from the surface of the water
    BRefraction of light as it passes from water into air
    CDispersion of light into colors by the water
    DScattering of light by tiny particles suspended in the water
  2. 2Question 2

    A ray of light passes obliquely from air into glass. Which way does it bend?

    AAway from the normal
    BIt passes straight through without bending
    CTowards the normal
    DBack into the air
  3. 3Question 3

    The refractive index of glass is 1.5 and the speed of light in air is 3 × 10⁸ m/s. What is the speed of light in the glass?

    A4.5 × 10⁸ m/s
    B2 × 10⁸ m/s
    C1.5 × 10⁸ m/s
    D3 × 10⁸ m/s
  4. 4Question 4

    Which statement is Snell's law of refraction?

    AThe angle of incidence is equal to the angle of refraction
    BThe ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media
    CThe incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane, on the same side of the normal
    DThe refracted ray always bends toward the normal
  5. 5Question 5

    The table gives the refractive index of four media. About how many times faster does light travel in water than in diamond?

    A table of four media and their refractive indices: water 1.33, kerosene 1.44, crown glass 1.52 and diamond 2.42.
    AAbout 0.55 times
    BAbout 3.75 times
    CAbout 1.1 times
    DAbout 1.8 times
  6. 6Question 6

    The diagram shows an object placed beyond 2F in front of a convex lens. Where is the image formed, and what is it like?

    A convex lens on a principal axis with F and 2F marked on both sides. An upright arrow object stands beyond 2F on the left, with two principal rays drawn from its tip through the lens. No image is drawn.
    ABetween F and 2F on the other side, real, inverted and diminished
    BBeyond 2F on the other side of the lens, real, inverted and highly magnified
    CAt 2F on the other side, the same size
    DOn the same side as the object, virtual and erect
  7. 7Question 7

    The diagram shows an object placed between the optical center and F of a convex lens. Where is the image formed, and what is it like?

    A convex lens on a principal axis with F and 2F marked on both sides. An upright arrow object stands between the lens and F on the left, with two principal rays drawn from its tip. No image is drawn.
    ABeyond 2F on the other side, real and inverted
    BAt infinity
    COn the same side as the object, virtual, erect and magnified
    DBetween F and 2F on the other side of the lens, real, inverted and diminished
  8. 8Question 8

    The diagram shows an object in front of a concave lens. Where is the image formed, and what is it like?

    A concave lens on a principal axis with F and 2F marked on both sides. An upright arrow object stands on the left, with two principal rays drawn from its tip through the lens. No image is drawn.
    AOn the other side of the lens between F and 2F, real, inverted and slightly diminished
    BBetween F and the optical center on the same side, virtual, erect and diminished
    CAt 2F on the same side, virtual and magnified
    DAt F on the other side, highly diminished
  9. 9Question 9

    The diagram shows an object placed exactly at 2F in front of a convex lens. Where is the image formed, and what is it like?

    A convex lens on a principal axis with F and 2F marked on both sides. An upright arrow object stands exactly on the 2F mark on the left, with two principal rays drawn from its tip. No image is drawn.
    AAt F on the other side, diminished
    BAt 2F on the other side, real, inverted and the same size
    CBeyond 2F on the other side of the lens, real, inverted and magnified
    DAt 2F on the same side, virtual and erect
  10. 10Question 10

    A ray of light passes through a rectangular glass slab. How does the emergent ray compare with the incident ray?

    AIt is parallel to the incident ray but shifted sideways
    BIt bends toward the normal and stays bent
    CIt is deviated by exactly twice the angle of incidence at the first face
    DIt is reflected back along its own path
  11. 11Question 11

    To use a convex lens as a magnifying glass, where must the object be placed?

    AAnywhere beyond 2F on the principal axis
    BBetween F and 2F
    CBetween the optical center and F
    DExactly at F
  12. 12Question 12

    A lens is thicker at the edges than in the middle. What kind of lens is it, and what does it do to parallel rays?

    AA convex lens; it converges them to a single point called the principal focus
    BA plane lens; it leaves them parallel
    CA concave lens; it diverges them so they appear to come from a focus
    DA convex lens; it diverges them

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