Science
(a) What is dispersion of light?
(b) Explain the condition under which dispersion happens?
(c) Give one reason that causes presbyopia.
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Answer
(a) Dispersion of light is the phenomenon in which white light separates into its component colours (spectrum) when it passes through a medium, such as a prism. Different colours of light bend through different angles with respect to incident light, thus becoming distinct.
(b) Dispersion occurs when light passes from one medium to another where the speed of light is different for each wavelength. For example, in a prism, each colour of light has a different refractive index due to varying wavelengths, causing each colour to bend at different angles as they exit the prism. Dispersion only happens if the medium has a variable refractive index across different wavelengths, like glass or water.
(c) Presbyopia is caused by the gradual loss of flexibility in the lens of the eye, which occurs with aging. This reduced flexibility prevents the lens from changing shape effectively to focus on close objects, making it difficult to see them clearly.
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