What is the frequency, in hertz, of an electromagnetic wave with a wavelength of 625 nm?

- Frequency is .

Solution:- The wavelength of electromagnetic radiation is given as 625 nm and we are asked to calculate the frequency. Frequency is inversely proportional to the wavelength and the formula used to calculate frequency when wavelength is given is:

where, is frequency, c is speed of light and is the wavelength.

Value of speed of light is . We need to convert the given wavelength from nm to m.

So,

=

Let's plug in the values in the formula and calculate the frequency:

= or Hz.

So, the frequency of the electromagnetic wave is .

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e