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THIRD TERM EXAMINATION 2024/2025 ACADEMIC YEAR
Physics(SS2)
1. If the angle of reflection of a propagated ray is 35°, calculate (a) The angle of deviation (b) The angle of glance (c) Angle of incidence.
2. An object is placed between two mirrors inclined at an angle 40 to each other. Find the number of images that will be formed.
3. Which of the following statements is untrue?
When an image is formed in a plane mirror, the image formed will be
(a) the same size as the object (b) smaller than the object (c) laterally inverted (d) always virtual
4. In which of the following instrument is the image that is formed erect
pin hole camera (b) simple camera (c) microscope (d) periscope
5. A body that produces its own light is said to be (a) luminous (b)non- incandescent (c) opaque (d) translucent
Answer (1)
The angle of deviation is calculated using the formula 18 0 ∘ − 2 × angle of incidence , which gives 11 0 ∘ .
The angle of glance is calculated using 9 0 ∘ − angle of incidence , resulting in 5 5 ∘ .
The angle of incidence equals the angle of reflection, which is 3 5 ∘ .
The number of images formed is calculated using ( angle between mirrors 360 ) − 1 , which gives 8 .
Explanation
Problem Analysis We are given the angle of reflection as 3 5 ∘ . We need to find the angle of deviation, the angle of glance, and the angle of incidence. We also need to determine the number of images formed by two mirrors inclined at 4 0 ∘ , identify the untrue statement about plane mirror images, identify the instrument forming an erect image, and name the term for a body producing its own light.
Angle of Deviation Calculation (a) The angle of deviation is the angle through which the light ray is deflected from its original path. It is calculated as 18 0 ∘ − 2 × angle of incidence . Since the angle of incidence equals the angle of reflection, the angle of incidence is 3 5 ∘ . Therefore, the angle of deviation is 18 0 ∘ − 2 × 3 5 ∘ = 18 0 ∘ − 7 0 ∘ = 11 0 ∘ .
Angle of Glance Calculation (b) The angle of glance is the angle between the incident ray and the surface of the mirror. It is calculated as 9 0 ∘ − angle of incidence . Therefore, the angle of glance is 9 0 ∘ − 3 5 ∘ = 5 5 ∘ .
Angle of Incidence Determination (c) The angle of incidence is equal to the angle of reflection, which is given as 3 5 ∘ .
Number of Images Calculation The number of images formed by two mirrors inclined at an angle θ is given by the formula n = θ 36 0 ∘ − 1 . In this case, θ = 4 0 ∘ , so the number of images formed is n = 4 0 ∘ 36 0 ∘ − 1 = 9 − 1 = 8 .
Untrue Statement Identification When an image is formed in a plane mirror, it is always the same size as the object, laterally inverted, and virtual. Therefore, the untrue statement is that the image is smaller than the object.
Instrument with Erect Image Identification A periscope forms an erect image. A pinhole camera and a simple camera form inverted images. A microscope also forms an inverted image.
Luminous Body Identification A body that produces its own light is said to be luminous.
Final Answer Summary
(a) The angle of deviation is 11 0 ∘ .
(b) The angle of glance is 5 5 ∘ .
(c) The angle of incidence is 3 5 ∘ .
The number of images formed is 8.
The untrue statement is (b) smaller than the object.
The instrument that forms an erect image is (d) periscope.
A body that produces its own light is said to be (a) luminous.
Examples
Understanding reflection and image formation is crucial in designing optical instruments like periscopes and telescopes. For instance, knowing how multiple reflections work helps engineers create periscopes that allow people to see over obstacles. Similarly, the principles of reflection are used in designing car mirrors to provide a clear and accurate view of the surroundings, enhancing safety.
