The answer is (1) 90 Sr. The definition of beta decay is that a type of radioactive decay in which one proton will change to one neutron and release one electron inside the nucleus. And 90Sr is a common beta emitter.
Answer:
Helium
Explanation:
LOOK AT THE TABLE OF ELEMENTS WOMAN!!!
Answer : The de Broglie wavelength will be 
Solution :
The formula used for de Broglie wavelength is:
..........(1)
where,
= wavelength = ?
h = Planck's constant = 
m = mass = 1.2 g = 0.0012 kg
Conversion used : 1 kg = 1000 g
v = velocity = 150 m/s
Now put all the given values in equation 1, we get:


Therefore, the de Broglie wavelength will be 