Wave length measures the width of the wave
Answer:
B
Explanation:
I am not sure but I think it is B. Out of all the answers that one makes sense.
Answer:
it is always necessary to use the roman numeral as the assigned charge of the metal.
Explanation:
This is so that one would know which Transition metal is being used. For example copper (II) would be Cu²+
Picometre is equal to 1·10⁻¹²m
175·10⁻¹² m = 1,75·10⁻¹⁰ m
Answer:- D. Double- replacement reaction
Explanations:- In general, the decomposition reactions looks like:

The given reaction looks different than this and so it is not decomposition reaction.
A single-replacement reaction looks like:

Our reaction looks different from this so single-replacement is also not correct.
Synthesis reaction looks exactly opposite to decomposition reaction.

The given reaction is different than this and so it is not synthesis reaction also.
A double-replacement reaction looks like:

In this reaction, the ions are exchanged as could be seen in the general reaction. On reaction side,A is with B and C is with D. On product side, A is with D and C is with B.
The same is happening in the given reaction. Nitrate ion is with lead metal on reactant side and chlorine is with hydrogen, On product side, Chlorine is with lead metal and nitrate ion is with hydrogen. So, ion exchange has taken place here and so this is a double-replacement reaction and choice D is correct.