Question

    Consider the following statements: Assertion (A):

    In the visible spectrum of light, red light has more energy than green light. Reason (R): The wavelength of red light is greater than that of green light. Choose the correct answer from the codes given below:
    A Both A and R are true, and R is the correct explanation of A. Correct Answer Incorrect Answer
    B Both A and R are true, but R is not the correct explanation of A. Correct Answer Incorrect Answer
    C A is true, but R is false. Correct Answer Incorrect Answer
    D A is false, but R is true. Correct Answer Incorrect Answer

    Solution

    • Red light has a longer wavelength compared to green light; thus, Reason (R) is correct. • However, energy is inversely proportional to wavelength (E ∝ 1/λ). This means shorter wavelength light has more energy than longer wavelength light. • Therefore, green light has more energy than red light, making Assertion (A) false. Thus, the correct answer is (d) A is false, but R is true.  Energy of light is given by the formula E = hν = hc/λ, where h = Planck’s constant, ν = frequency, c = speed of light, and λ = wavelength.  In the visible spectrum, violet light has the highest energy, and red light has the lowest.  Wavelength order (longest to shortest): Red > Orange > Yellow > Green > Blue > Indigo > Violet.  Energy order (lowest to highest): Red < Orange < Yellow < Green < Blue < Indigo < Violet.  Green light has a shorter wavelength than red, so it carries more energy.  Red light is used in night vision equipment because of its low energy and low scattering property.  Green light is more energetic and is often used in applications like laser pointers and signaling.

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