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  4. Many exoplanets have been discovered by the transit method, where in one monitors, a dip in the intensity of the parent star as the exoplanet moves in front of it. The exoplanet has a radius R and the parent star has radius 100 R. If I0 is the intensity observed on earth due to the parent star, then as the exoplanet transits

Q. Many exoplanets have been discovered by the transit method, where in one monitors, a dip in the intensity of the parent star as the exoplanet moves in front of it. The exoplanet has a radius and the parent star has radius . If is the intensity observed on earth due to the parent star, then as the exoplanet transits

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Solution:

Intensity of radiation (mainly visible light) emitted from surface of a star is proportional to its area
So, or
where, k = constant
Now, if = intensity of parent star
Then,
When exoplanet is in front of star, observed intensity will be minimum. Let intensity minimum is , then




So,

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