The wavelength of light that has a frequency of 2.40x10^13 s-1 .

Wavelength and Frequency are inversely related to each other as,

                                       υ  =  c / λ    (1)
Where;
           υ  =  Frequency  =  2.40 × 10¹³ s⁻¹

           c  =  2.99 × 10⁸ ms⁻¹

           λ  =  ?

Solving equation 1 for λ,

                                     λ  =  c / υ

Putting Values,
                                     λ  =  2.99 × 10⁸ ms⁻¹ ÷ 2.40 × 10¹³ s⁻¹

                                     λ  =  0.00001245833 m
Or,
                                     λ  =  1.24 × 10⁻⁵ m

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

Ions gain or lose electrons