Wavelength is the
ratio of speed of light and frequency:
wavelength = speed of
light / frequency
where frequency is: (c
is speed of light)<span>
freq = c / wavelength = 3E8/550E-9 = 5.45E14 Hz
We know that photons have energy E = hf = 6.626E-34 Js * 5.45E14
Hz = 3.61 E-19 J
Therefore if it has 4.40 mJ of energy, the pulse has:
<span>4.40E-3/3.61E-19 = 1.22E16 photons</span></span>
Answer:
letter b by replicating experiments
Explanation:
The mass number = protons + neutrons. Bromine has a mass number of 80<span> and 35 protons so </span>80<span>-35 = </span>45<span> neutrons. b) How many electrons does the neutral atom of bromine have? The neutral atom of bromine has 35 electrons because the number of electrons equals the number of protons.</span>
Answer:
chemical change
Explanation:
burning and cooking are both chemical changes.
Answer: There are 
atoms of hydrogen are present in 40g of urea, 
.
Explanation:
Given: Mass of urea = 40 g
Number of moles is the mass of substance divided by its molar mass.
First, moles of urea (molar mass = 60 g/mol) are calculated as follows.
According to the mole concept, 1 mole of every substance contains 
atoms.
So, the number of atoms present in 0.67 moles are as follows.
In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.
Thus, we can conclude that there are atoms of hydrogen are present in 40g of urea, .
