Chapter 7.10, Problem 1P

a.

To determine

To find the number of kilometers in a year.

Answer to Problem 1P

  $9.4608\times {10}^{12}\text{ km}$

Explanation of Solution

Given:

The light travels at the rate of $3\times {10}^5$ km/sec. Assume a year has $365$ days.

Calculation:

The total distance in year will be

  $\begin{array}{l}3\times {10}^5\times 365\times 24\times 3600km\\ =9.4608\times {10}^{12}\text{ km}\end{array}$

b.

To determine

To find the distance in kilometers.

Answer to Problem 1P

  $\text{14}\text{.1912}\times {\text{10}}^{18}\text{km}$

Explanation of Solution

Given:

The Andromeda Galaxy is approximately $1.5\times {10}^6$ light years from the earth.

Calculation:

The distance in kilometers will be-

  $\begin{array}{l}9.4608\times {10}^{12}\times 1.5\times {10}^6\text{km}\\ \text{=14}\text{.1912}\times {\text{10}}^{18}\text{km}\end{array}$

c.

To determine

To find how long will it take the light to reach from star to earth.

Answer to Problem 1P

  $4.3$ Years.

Explanation of Solution

Given:

The distance from earth to Alpha Centaury star is $1.5\times {10}^6$ light years from the earth.

Calculation:

The time taken will be

  $=\frac{4.07\times {10}^{13}}{9.4608\times {10}^{12}}=0.43\times 10=4.3$

d.

To determine

To find how long will it take the light to reach from Sun to earth.

Answer to Problem 1P

  $5\times {10}^2\sec$

Explanation of Solution

Given:

The sun is $1.5\times {10}^8$ km from the earth.

Calculation:

The time taken will be-

  $\begin{array}{l}\frac{1.5\times {10}^8}{3\times {10}^5}\\ =0.5\times {10}^3\\ =5\times {10}^2\sec \end{array}$