Sound waves can be used in a similar way to "see" things. After turning on a sound source, we can look at the pattern of reflected sound waves that bounce back to us. Our own ears and brain don't process sound into mental pictures.
answer:
The answer to this specific riddle is silence.
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Answer:
(a) 
(b) 15 hours
Explanation:
half life, T = 12 hours
No = 19 g
(a) Let N be the amount remaining after time t.
Let λ be the decay constant.

The equation of radioactivity used here is given by


(b) N = 8 gram
Substitute the values in above equation

λ = 0.0577 per hour
So, 

Take natural log on both the sides
- 0.0577 t = - 0.865
t = 15 hours
Answer:
B please give me brainlyest
Explanation: