Below are four statements about electromagnetic waves.
1 Microwaves have a smaller wavelength than visible light.
2 The speed of visible light in a vacuum is higher than the speed of other types of electromagnetic wave.
3 Gamma rays have the largest wavelength of any electromagnetic wave.
4 Radio waves are used in hospital radiography to look for broken bones.
Which of the statements are correct?

Answer:

3) D

We need to calculate the difference in mass numbers and atomic numbers.

Mass number of U = 238
Sum of mass number of products Sr and Xe = 95 + 139 = 234

Atomic number of U = 92
Sum of atomic numbers of products Sr and Xe = 38 + 54 = 92

Atomic number is same, meaning that no protons are emitted. Since the mass number decreases by 4 and no protons are given off, 4 neutrons must have been emitted