What is the frequency of light for which the wavelength is 7.1 × 102 nm?

2.4 × 10 −6 s −1

2.1 × 102 s −1

4.2 × 105 s −1

4.2 × 1014 s −1

4.2 × 10⁻¹⁴s⁻¹

Explanation:

Given parameters:

Wavelength of light = 7.1 x 10²nm

We simplify and express this value in metres(m) to give:

⇒7.1 x 10² x 10⁻⁹m = 7.1 x 10⁽⁻²⁺⁹⁾ m

= 7.1 x 10⁷m

The wavelength is 7.1 x 10⁷m

We use the formula V = fλ

We know that Velocity of light is 3 x 10⁸ms⁻¹

Making f, frequency the subject of the formula gives :

f = V/λ

f = 3 x 10⁸ms⁻¹ / 7.1 x 10⁷m

f = 4.2 x 10⁻¹⁴s⁻¹

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.