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Rainbow is produced when sunlight falls on drops of rain. Which of the following physical
phenomena are responsible for this?
(1). Dispersion
(2). Refraction
(3). Internal Reflection
Select the correct answer using the codes given below.

(a)

1 and 2 only

(b)

2 and 3 only

(c)

1 and 3 only

(d)

1, 2 and 3

Correct Answer

(d)

Explanation

Option:-1
Each individual droplet of water acts as a tiny prism that both
disperses the light and reflects it back to our eye.
Option:-2
Since water is more dense than air, light is refracted as it enters
the drop.
Option:-3
Some of the light will reflect off the back of the drop if the angle is
larger than the critical angle (48° for water).

Microtheme: PhysicsXLight energy —
8 questions asked in Prelims in the past.

  1. [2021] With reference to street lighting, how do sodium lamps differ from LED lamps?
    1.Sodium lamps produce light in 360 degrees, but it is not so in the case of LED lamps.
    2.As streetlights, sodium lamps have a longer lifespan than LED lamps.
    3.The spectrum of visible light from sodium lamps is almost monochromatic, while LED lamps offer significant color advantages in street lighting.
    Select the correct answer using the code given below:

    • (a) 3 only
    • (b) 2 only
    • (c) 1 and 3 only
    • (d) 1, 2, and 3
    Correct Answer: (C) 1 and 3 only
  2. [2018] Consider the following phenomena :
    1. Light is affected by gravity.
    2. The Universe is constantly expanding.
    3. Matter warps its surrounding space-time.
    Which of the above is/are the prediction/predictions of Albert Einstein’s General Theory of Relativity, often discussed in media?

    • (a) 1 and 2 only
    • (b) 3 only
    • (c) 1 and 3 only
    • (d) 1, 2 and 3
    Correct Answer: (D) 1, 2 and 3
  3. [2017] Organic Light Emitting Diodes (OLEDs) are used to create digital display in many devices. What are the advantages of OLED displays over Liquid Crystal displays?
    1. OLED displays can be fabricated on flexible plastic substrates.
    2. Roll-up displays embedded in clothing can be made using OLEDs.
    3. Transparent/displays are possible using OLEDs
    Select the correct answer using the code givenbelow :

    • (a) 1 and 3 only
    • (b) 2 only
    • (c) 1, 2 and 3
    • (d) None of the above statements is correct
    Correct Answer: (C) 1, 2 and 3
  4. [2013] Rainbow is produced when sunlight falls on drops of rain. Which of the following physical
    phenomena are responsible for this?
    (1). Dispersion
    (2). Refraction
    (3). Internal Reflection
    Select the correct answer using the codes given below.

    • (a) 1 and 2 only
    • (b) 2 and 3 only
    • (c) 1 and 3 only
    • (d) 1, 2 and 3
    Correct Answer: (D) 1, 2 and 3
  5. [2013] Conside the following phenomena :
    (1). Size of the sun at dusk
    (2). Colour of the sun at dawn
    (3). Moon being visible at dawn
    (4). Twinkle of stars in the sky
    (5). Polestar being visible in the sky
    Which of the above are optical illusions?

    • (a) 1, 2 and 3
    • (b) 3, 4 and 5
    • (c) 1, 2 and 4
    • (d) 2, 3 and 5
    Correct Answer: (C) 1, 2 and 4
  6. [2011] What is the difference between a CFL and a LED lamp? 1. To produce light, a CFL uses mercury vapour and phosphor while an LED lamp uses semiconductor material. 2. The average lifespan of a CFL is much longer than that of a LED lamp. 3. A CFL is less energy efficient as compared to an LED lamp.

    • (a) 1 only
    • (b) 2 and 3 only
    • (c) 1 and 3 only
    • (d) 1, 2 and 3
    Correct Answer: (C) 1 and 3 only
  7. [2009] Which one among the following has the highest energy ?

    • (a) Blue light
    • (b) Green light
    • (c) Red light
    • (d) Yellow light
    Correct Answer: (A) Blue light
  8. [2008] Assertion (A): In the visible spectrum of light, red light is more energetic than green light.
    Reason (R): The wavelength of red light is more than that of green light.

    • (a) Both A and R are individually true and R is the correct explanation of A
    • (b) Both A and R are individually true and R is not the correct explanation of A
    • (c) A is true but R is false
    • (d) A is false but R is true
    Correct Answer: (D) A is false but R is true