According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?

A) Its apparent brightness will decrease by a factor of 9.
B) Its apparent brightness will increase by a factor of 9.
C) Its apparent brightness will decrease by a factor of 3.
D) Its apparent brightness will increase by a factor of 3.


A) Its apparent brightness will decrease by a factor of 9.

Physics & Space Science

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Fill in the blank(s) with the appropriate word(s).

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Stellar spectra started with the amount of hydrogen found in the star's spectrum and started with the letters A through Q. What are the current letters used to classify stellar spectra?

What will be an ideal response?

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An electron moves with a speed of 3.0 × 104 m/s perpendicular to a uniform magnetic field of 0.40 T. What is the magnitude of the magnetic force on the electron?

A) 4.8 × 10-14 N B) 1.9 × 10-15 N C) 5 × 10-20 N D) 2.2 × 10-24 N E) zero

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The atmosphere becomes opaque to infrared radiation when it

A) increases in temperature. B) contains excess water vapor and carbon dioxide. C) radiates high-frequency radiation. D) none of the above

Physics & Space Science