I have a couple of questions regarding DNA or RNA extraction in the laboratory.

1. Why is the DNA or RNA sample diluted in water or in a buffer to 1ml prior to putting the sample in the spectrophometer?

2. In spectrophotometric conversions for nucleic acids:
For dsDNA, an A260 of 1 = 50 µg/ml
For ss oligonucleotides, an A260 of 1 = 33 µg/ml
For ssRNA, an A260 of 1 = 40 µg/ml
My question is: are these values (55, 33 and 40 µg/ml) standard, i mean, the same at all times for Absorbance at 260 nm?
And what is meant by "Absorbance 260 of 1" What is the meaning of "1" ?

Question

I have a couple of questions regarding DNA or RNA extraction in the laboratory.

1. Why is the DNA or RNA sample diluted in water or in a buffer to 1ml prior to putting the sample in the spectrophometer?

2. In spectrophotometric conversions for nucleic acids:
For dsDNA, an A260 of 1 = 50 µg/ml
For ss oligonucleotides, an A260 of 1 = 33 µg/ml
For ssRNA, an  A260 of 1 = 40 µg/ml
My question is: are these values (55, 33 and 40 µg/ml) standard, i mean, the same at all times for Absorbance at 260 nm?
And what is meant by "Absorbance 260 of 1" What is the meaning of "1" ?