The atomic number of an atom says how many protons it has. This number cant change, since the atomic number is what gives elements their identities (in the periodic table, at least).
The mass number, on the other hand, says how many protons AND neutrons the atom has (so, the sum of P+ and N0). So, electrons have nothing to do with this number.
Atoms are neutrally charged, which means there has to be an equal number of positive and negative particles. The negative particles of an atom are its electrons, and since our atom has 4 protons, it must also have 4 electrons.
Answer: 
Explanation:
The diffraction angles 
when we have a slit divided into 
parts are obtained by the following equation:
(1)
Where:
is the width of the slit
is the wavelength of the light
is an integer different from zero.
Now, the second-order diffraction angle is given when 
, hence equation (1) becomes:
(2)
Now we have to find the value of 
:
(3)
Then:
(4)
(5)
Finally:
(6)
Answer:
A box sits stationary on a ramp
Explanation:
Static friction is a force which keeps an object at rest as it is in the case of the box. It has to be overcome for the object to be set into motion.
Static force of friction is calculated as follows:
F= μη
F is static force of friction.
μ is the coefficient of static friction.
η is the normal force.
Answer:
The time elapses until the boat is first at the trough of a wave is 4.46 seconds.
Explanation:
Speed of the wave, v = 59 km/h = 16.38 m/s
Wavelength of the wave, 
If f is the frequency of the wave. The frequency of a wave is given by :
The time period of the wave is given by :
We need to find the time elapses until the boat is first at the trough of a wave. So, the time will be half of the time period of the wave.
Hence, this is the required solution.
