Answer in brief, any one question. a. The sun is less bright in morning and evening as compared to that at noon although its distance from the observer is almost the same. Why? [2] b. When white…

a. The sun appears less bright in the morning and evening because sunlight reaches the observer at a larger angle (θ) from the vertical (zenith). The intensity of sunlight is proportional to sin θ, where θ is the angle between the sun’s rays and the normal to Earth’s surface. At noon, θ ≈ 0°, so sin θ = 1 (maximum brightness). As the sun rises or sets, θ increases (e.g., 45° at dawn/dusk), reducing sin θ and thus the apparent brightness. Additionally, sunlight passes through more of Earth’s atmosphere at oblique angles, causing scattering and absorption by air molecules and dust, further dimming the light.

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b. When white light passes through a prism, refraction occurs due to the prism’s dispersive power (variation of refractive index with wavelength). The refractive index $n$ of glass is higher for violet light (shorter wavelength, ~400 nm) than for red light (longer wavelength, ~700 nm). According to Snell’s law ($n_1\sin {\theta }_1=n_2\sin {\theta }_2$), violet light is bent more than red light, deviating toward the base of the prism. Conversely, red light, with a lower refractive index, is bent the least and appears at the top of the spectrum. This wavelength-dependent refraction is called dispersion.