Light: Mirrors and Lenses — Mastery

Q1. The shape of a spherical mirror is best thought of as

• A. A flat disc of glass
• B. A part of an imaginary hollow sphere
• C. A cylinder cut along its length
• D. A solid metal cone

Q2. The outline of the surface of a concave or convex spherical mirror is

• A. Square
• B. Triangular
• C. Circular
• D. Star-shaped

Q3. In the schematic representation of a concave or convex mirror, the non-reflecting surface is shown

• A. Shaded (with hatching lines)
• B. Coloured red
• C. With an arrow
• D. As a dashed circle

Q4. A student moves an object slowly away from a concave mirror, watching the image. The correct order of changes the student will observe is

• A. Erect–enlarged → erect–same size → inverted–enlarged → inverted–diminished
• B. Inverted–enlarged → erect–enlarged → erect–diminished
• C. Erect–enlarged → inverted–enlarged → inverted–diminished
• D. Inverted–diminished → erect–enlarged → erect–same size

Q5. Most modern reflecting telescopes use as their main (primary) mirror a

• A. Large plane mirror
• B. Large concave mirror
• C. Large convex mirror
• D. Magnifying lens only

Q6. Big stores install convex mirrors near the ceiling to monitor a large area mainly because these mirrors

• A. Form an inverted image of customers
• B. Magnify objects for easier identification
• C. Cover a wider area than a plane mirror of the same size
• D. Reflect ultraviolet light to deter theft

Q7. When an object is gradually moved away from a convex mirror, the image

• A. Becomes inverted after a certain distance
• B. Stays erect but its size decreases slightly
• C. Becomes very large and then inverts
• D. Stays exactly the same size at all distances

Q8. Lateral inversion of the image is seen in

• A. Only plane mirrors
• B. Only concave mirrors
• C. Only convex mirrors
• D. All three — plane, concave and convex mirrors

Q9. In Fig. 10.27 of the chapter, object O is shown with the image I formed by mirror M. In figure (a), I is the same size as O. In figure (b), I is larger than O. Which is correct?

• A. (a) is a plane mirror and (b) is a concave mirror.
• B. (a) is a convex mirror and (b) is a concave mirror.
• C. (a) is a concave mirror and (b) is a convex mirror.
• D. (a) is a plane mirror and (b) is a convex mirror.

Q10. The ray of light that comes back from the mirror after striking it is called the

• A. Incident ray
• B. Normal ray
• C. Reflected ray
• D. Bent ray

Q11. The normal to a mirror at the point of incidence is

• A. A line lying along the mirror surface
• B. A line at 90° to the mirror surface at that point
• C. The same as the incident ray
• D. A line at 45° to the mirror

Q12. In Activity 10.5 (bent paper sheet), when the bent portion of the sheet is straightened again, the reflected beam

• A. Stays disappeared
• B. Becomes brighter than before
• C. Reappears at the same position
• D. Falls on a different mirror

Q13. Which of the following best describes the geometry of reflection at a single point?

• A. The incident ray and the mirror surface are in one plane only.
• B. The reflected ray lies on the opposite side of the mirror surface.
• C. The incident ray, the normal and the reflected ray all lie in one plane.
• D. The normal is always parallel to the incident ray.

Q14. When a parallel beam reflects off a spherical mirror, each individual ray

• A. Ignores the laws of reflection because the surface is curved
• B. Still obeys i = r at the point where it strikes
• C. Reflects only if i = 0
• D. Becomes part of a single combined ray

Q15. In Activity 10.6, multiple parallel beams of light are produced by

• A. A single covered slit of the comb
• B. Leaving many openings of the comb uncovered
• C. Removing the torch and using sunlight
• D. Stacking three mirrors at right angles

Q16. Which statement about images formed by a concave mirror is correct?

• A. The image is always inverted, irrespective of object distance.
• B. The image is always erect and diminished.
• C. The image is always the same size as the object.
• D. The image may be erect or inverted, and enlarged, diminished or of the same size, depending on the object's distance.

Q17. According to the Snapshots, the characteristics of a concave-mirror image depend on

• A. The colour of the object
• B. The size of the mirror only
• C. The room's brightness
• D. The distance of the object from the mirror

Q18. Devices that use mirrors and lenses to concentrate sunlight into a small area are called

• A. Light bulbs
• B. Periscopes
• C. Kaleidoscopes
• D. Solar concentrators

Q19. Solar furnaces, mentioned in the chapter, are powerful enough to

• A. Light a small LED only
• B. Boil one glass of water in an hour
• C. Charge a mobile phone
• D. Melt steel

Q20. A Class 8 teacher plans Activity 10.7 (focusing sunlight with a concave mirror) for a school yard. The single most important safety instruction to give students before starting is

• A. Wear comfortable shoes for the activity.
• B. Stand in a single file while observing.
• C. Use a piece of newspaper rather than chart paper.
• D. Do not look at the Sun or at the mirror reflecting it; focus only on paper, never on faces or eyes.

Q21. Like mirrors, lenses can also be of two main shapes

• A. Square and rectangular
• B. Translucent and opaque
• C. Hot and cold
• D. Convex and concave

Q22. Which of the following uses a convex lens to perform its main function?

• A. A flat window pane
• B. A periscope's plane mirrors
• C. An ambulance siren
• D. A camera, a telescope, a microscope and even the human eye

Q23. In Activity 10.11, a convex lens replaces a concave mirror in the path of sunlight. Paper held below the lens at the right distance

• A. Does nothing — only mirrors can burn paper
• B. Becomes wet because the lens condenses moisture
• C. Starts to glow but never burns
• D. Begins to burn because the lens converges sunlight to a small bright spot

Q24. Eyeglasses (chashma) worn by some people contain lenses. Among the everyday uses of lenses described in the chapter, eyeglasses are listed because

• A. They protect the eyes from heat only
• B. They reflect light away from the eye
• C. They are simply decorative items
• D. Their lenses help the wearer see clearly

Q25. Multiple parallel beams of light pass through a concave lens. After passing through, the beams

• A. Converge to a single point
• B. Stay perfectly parallel
• C. Vanish behind the lens
• D. Spread out — they diverge

Q26. According to the "Our scientific heritage" box, more than 800 years ago, during the time of Bhāskara II, Indian astronomers used to observe stars and planets by looking at their reflections in

• A. Shallow bowls of water
• B. Polished metal mirrors fixed on the ground
• C. Convex lenses mounted on tall towers
• D. Modern reflecting telescopes

Q27. A teacher assigns the "Discover, design, and debate" project where students visit an ENT specialist or dentist and identify the mirror used. The most useful guiding question for the visit is

• A. What is the doctor's daily schedule?
• B. How is the clinic decorated?
• C. How much does the consultation cost?
• D. Is the mirror flat, curved inward, or curved outward — and is the image enlarged, same size, or diminished?

Q28. Before doing Activity 10.1 (image in a metal spoon) with Class 8 students, the most effective pedagogic step is to

• A. Ask students to first predict what the image will look like on each side of the spoon, then observe.
• B. Show the final result on a screen and skip the activity.
• C. Read out the Snapshots aloud first.
• D. Give each student a written test on mirrors.

Q29. A Class 8 student says, "Lenses and mirrors are the same thing because both can make objects look bigger." Which clarification is most accurate?

• A. Lenses and mirrors are exactly the same; the words are interchangeable.
• B. Lenses can magnify but mirrors cannot.
• C. Mirrors can magnify but lenses cannot.
• D. Both can magnify, but lenses transmit light while mirrors reflect it — we see through a lens but in a mirror.

Q30. From a constructivist standpoint, the best opening for the chapter "Light: Mirrors and Lenses" in a Class 8 classroom is to

• A. Begin with the laws of reflection on the blackboard.
• B. Hand out the Snapshots before any activity.
• C. Start by defining concave and convex mirrors.
• D. Recall what students already know about images in a plane mirror from Class 7 and then ask them to look at their image in a metal spoon.