Why is the relay in the circuit I built make a noise?

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Guys I have made an automatic light circuit for my college project and I have used an amplifier, a relay and LDR in it…

The circuit is working as well as expected. During the daytime the lightbulb does not glow and at night it turns on automatically. However, when the light turns on the relay starts making noise… Is there a problem in the circuit like a short circuit or anything like that? What should I do to get rid of the noise? My teacher will say it’s noisy… : (

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