Alpha particles have both high mass and low velocity, but it would be the former that determines why they can't penetrate. An alpha particle is made of two protons and two neutrons, which is quite a large mass for a particle. This large mass keeps it from penetrating too deeply into anything, since it will essentially "get stuck" when it comes too near to another atom.
So the answer, I believe, is B. Alpha particles have high mass.
Weight = mg, g ≈ 9.8 m/s²
Weight = 2.2 * 9.8 ≈ 21.56 N
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Answer:
Option C
Explanation:
Given:
- Depth of tissue d = 12 cm
- frequency of ultrasound f = 1 MHz
- Input Intensity I_i = 1000 W/m^2
- attenuation coefficient soft tissue a = 0.54
Find:
- Out-put intensity at the required depth
Solution
- The amount of attenuation in (dB) with the progression of depth is given by:
Attenuation = a*f*d
Attenuation = 0.54*12*1
Attenuation = 6.48 dB
- The relation with attenuation and ratio of input and output intensity is given by:
Attenuation = 10*log_10 (I_i / I_o)
6.48 dB = 10*log_10 (I_i / I_o)
I_i / I_o = 10^(0.648)
I_o = 1000 / 10^(0.648)
I_o = 225 W/m^2
- Hence the answer is option C: I_o = 250 W/m^2