Answers by experts to all your home work questions with concepts and videos for better learning

Q1 Single Correct Easy

18 + 19

• A. 37
• B. 27
• C. 47
• D. 29

1 Verified Answer | Published on 19th 03, 2021

Q2 Single Correct Easy

23 + 34

• A. 57
• B. 67
• C. 54
• D. 53

1 Verified Answer | Published on 19th 03, 2021

Q3 Subjective Hard
Gravitation and other forces prevent Hubble’s-law expansion from taking place except in systems larger than clusters of galaxies. What If? Imagine that these forces could be ignored and all distances expanded at a rate described by the Hubble constant of $$22 \times 10^{-3}\,m/(s . ly)$$. (a) At what rate would the $$1.85m$$ height of a basketball player be increasing? (b) At what rate would the distance between the Earth and the Moon be increasing?

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q4 Subjective Hard
Use Stefan’s law to find the intensity of the cosmic background radiation emitted by the fireball of the Big Bang at a temperature of $$2.73\, K$$.

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q5 Subjective Hard
A star moving away from the Earth at $$0.280c$$ emits radiation that we measure to be most intense at
the wavelength $$500\,nm$$. Determine the surface temperature of this star.

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q6 Subjective Hard
Difference countries establish different communication satellites in the orbits for their communication system. Are these orbits different ? Explain.

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q7 Subjective Hard
The energy required to excite an atom is on the order of $$1\,eV$$. As the temperature of the Universe dropped below a threshold, neutral atoms could form from plasma and the Universe became transparent. Use the Boltzmann distribution function $$e^{-E/k_BT}$$ to find the order of magnitude of the threshold temperature at which $$1.00\%$$ of a population of photons has energy greater than $$1.00\,eV$$.

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q8 Single Correct Hard
There are two ways to measure the brightness of a star; the apparent magnitude of the brightness of the star is the brightness seen from the earth and absolute magnitude of the brightness of the star which is the brightness of a star seen from the standard distance of ___________.
• A. $$10$$ parsec
• B. $$32.6$$ light years
• C. $$3.26$$ light years
• D. both (a) and (b)

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q9 Single Correct Hard
Two small balls having equal positive charge $$Q$$ (coulomb) on each are suspended by two insulating
strings of equal length $$L$$, from a hook fixed to a stand. If the whole set up is taken in a satellite
then the angle $$\theta$$ between the two strings is : (in equillibrium)
• A. $$O^{o}$$
• B. $$90^{o}$$
• C. $$180^{o}$$
• D. $$0 < \theta <180^{o}$$

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020

Q10 Single Correct Hard
Sky looks bright from the earth on a sunny day but from any space station it is dark becuase
• A. no reflection
• B. no luminous object
• C. no natural source
• D. eye deficiency

Asked in: Physics - Stars and the Solar System

1 Verified Answer | Published on 16th 11, 2020