Spectrum Quiz - ICSE Class 10 Physics

Free practice quiz: Spectrum (ICSE Class 10 Physics). 51 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. A prism with an apex angle of 60° is made of glass with a refractive index of 1.5. If a ray of light is incident on one face at an angle of incidence that results in minimum deviation, what is the angle of minimum deviation?

   1. 30°
   2. 37.2°
   3. 45°
   4. 60°
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   Answer: B. 37.2°

   For minimum deviation (δm), the angle of incidence (i) equals the angle of emergence (e), and the refracted ray inside the prism is perpendicular to the angle bisector. The formula for minimum deviation is δm = 2i - A, where A is the apex angle. Also, n = sin((A + δm)/2) / sin(A/2). Given A = 60° and n = 1.5, we have 1.5 = sin((60° + δm)/2) / sin(60°/2) = sin((60° + δm)/2) / sin(30°). 1.5 * sin(30°) = 0.75. So, sin((60° + δm)/2) = 0.75. (60° + δm)/2 = arcsin(0.75) ≈ 48.6°. Therefore, 60° + δm ≈ 97.2°, which gives δm ≈ 37.2°.

2. A ray of light passes through a convex lens. If the ray is parallel to the principal axis, after refraction, it will pass through:

   1. The optical center
   2. The principal focus on the other side
   3. The principal focus on the same side
   4. The center of curvature on the other side
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   Answer: B. The principal focus on the other side

   One of the principal rules for image formation by a convex lens is that a ray of light passing through the lens parallel to the principal axis, after refraction, converges at the principal focus on the opposite side of the lens.

3. The twinkling of stars is due to:

   1. The absorption of light by the Earth's atmosphere
   2. The reflection of starlight from celestial bodies
   3. The variation in the refractive index of the Earth's atmosphere
   4. The rotation of the Earth
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   Answer: C. The variation in the refractive index of the Earth's atmosphere

   The twinkling of stars is caused by the atmospheric refraction. Starlight travels through different layers of the atmosphere which have varying densities and temperatures, leading to fluctuations in the refractive index. This causes the path of light to bend continuously, making the star appear to twinkle.

4. The phenomenon of dispersion of white light by a prism is responsible for:

   1. The formation of a rainbow
   2. The bending of light towards the normal
   3. The scattering of light in the atmosphere
   4. The creation of a virtual image
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   Answer: A. The formation of a rainbow

   While dispersion by a prism is the fundamental principle, the formation of a rainbow involves dispersion of sunlight by water droplets in the atmosphere, along with reflection and refraction. The initial splitting of white light into its constituent colors by the prism is the core of dispersion.

5. Which of the following colors of visible light has the longest wavelength?

   1. Violet
   2. Green
   3. Red
   4. Blue
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   Answer: C. Red

   The visible spectrum of light consists of colors from violet to red, arranged in the order of increasing wavelength: Violet, Indigo, Blue, Green, Yellow, Orange, Red (VIBGYOR). Red light has the longest wavelength, and violet light has the shortest wavelength.

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