physics questions: light waves?

Question

1. How long would it take a radio signal to reach a star that is 9 light years away?
a. nine years, b. you need to know the wavelength, c. you need to know the frequency, or d. you need to know the speed

2. Which type of polarized sunglasses would help reduce glare the best?
horizontally polarized, vertically polarized, or diagonally polarized?

3. An astronomer ovserves the light coming from a distant star. He notices several distinct bright lines in the spectrum. What kind of spectrum is he observing?
absorption, red-shift, emission, polarization, or ultraviolet?

thanks for your help! =)

Answer 1

1. 9 years
2. Horizontally polarized
3. Emission spectra

Answer 2

1. How long would it take a radio signal to reach a star that is 9 light years away?
a. nine years, b. you need to know the wavelength, c. you need to know the frequency, or d. you need to know the speed

a. is the right answer. Radio signal is an electromagnetic radiation just as visible light and the velocity is same. 9 light years indicates the distance travelled by light in 9 years.

2. Which type of polarized sunglasses would help reduce glare the best?
horizontally polarized, vertically polarized, or diagonally polarized?

Off-hand, I am not able to answer this. We need to look into some good book on optics.

3. An astronomer ovserves the light coming from a distant star. He notices several distinct bright lines in the spectrum. What kind of spectrum is he observing?
absorption, red-shift, emission, polarization, or ultraviolet?

Emission spectrum is the right answer.


thanks for your help! =)

You are welcome.

Answer 3

1. nine years.

All EM radiation travels at the speed of light, from radio waves all the way up to gamma rays.

2. Diagonally polarized.

The electrical and magnetic waves that comprise light are 90 degrees from each other in orientation, so an electrical wave is vertical and a magnetic wave is horizontal. So if it's polarized vertically or horizontally only it'll allow one of the two waves through, if it's polarized diagonally it'll block both of them.

3. The astronomer would be observing absorption.

From the absorption lines on the spectrum he could figure out what elements the star happens to be made up of at the time of ovservation, as each element absorbs a certain wavelength of light and reflects all others.

Answer 4

1. nine years for radio signals to travel 9 light years
2. polarized sunglasses are normally vertically polarized
3. he is observing an emission spectrum coming from specific electron transitions

Regarding question 2, the viewing geometry for surfaces such as water and windshields of cars travelling toward or away from you partially reduces the amount of vertically polarized light which is reflected, due to Brewster angle effects. The reflected light has more horizontal polarization in it, so vertically polarized sunglasses block this horizontal polarization, reducing the glare.

Answer 5

Question #1 is poorly drafted: it fails to mention from which perspective is time to be measured. While the term "light year" refers to time as measured on earth, it cannot be assumed from the question that the frame of reference would be the same. Moving at the speed of light is something very different from astronomical measurements---one is a measurement of velocity while the other a measurement of distance. As the frame of reference changes or shifts so too does the dynamics of the question, making assumed correlation absurd.

Answer 6

1.t=x/v. x(9 light years)=9(3*10^8)364(24)(3600)

t=9(364)24(3600) nine years.choice (a) you didn't need to solve the question in this way...I wanted you to take it for granted.

Answer 7

if the Z velocity is severe adequate to penetrate the ZY line, than the ensuing image would be set by the parameters of the VT cube intersect and the DR+PR style. although, if SPRT is flat, then CC could be the optimal fee. and till the pc rotational is that of the sugar-unfastened type, it somewhat is going to be as much as RB to discover the lacking e book.