How many wavelengths are there now in one pulse?

[ravsau]

Homework Statement

A certain type of laser emits light that has a frequency of 5.1* 10^14 Hz. The light, however, occurs as a series of short pulses, each lasting for a time of 2.6* 10^-11 s. (a) How many wavelengths are there in one pulse? (b) The light enters a pool of water. The frequency of the light remains the same, but the speed of the light slows down to 2.3* 10^8 m/s. How many wavelengths are there now in one pulse?

Homework Equations

lamda= c/f

The Attempt at a Solution

I tried multiplying speed of electromagnetic wave with the time and divided by the freq but the answer is not correct. I am doing it online I just have 1 more chance left. Help!

 

[Redbelly98]

Welcome to physics forums.

What is the length (in meters) of the 2.6*10^-11s pulse?

What is the wavelength (also in meters)?