Question

the wavelength of red light in a spectrum is about 0.0000007 meters. which number best approximates this length as a power of 10?
a. $-7 \times 10^7$
b. $7 \times 10^{-6}$
c. $7 \times 10^7$
d. $7 \times 10^{-7}$

Explanation:

Step1: Recall scientific notation rules

Scientific notation is \(a\times10^{n}\), where \(1\leq|a|\lt10\) and \(n\) is an integer. For a number less than 1, \(n\) is negative, and \(n = -\) (number of places the decimal moves to the right to get \(a\) between 1 and 10).

Step2: Convert 0.0000007 to scientific notation

The number is 0.0000007. Move the decimal point 7 places to the right to get \(a = 7\) (since \(1\leq7\lt10\)). So \(n=-7\). Thus, \(0.0000007 = 7\times10^{-7}\).

Answer:

D. \(7\times10^{-7}\)