CO2 NaCl HCl These may all be classified as
2 answers:
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ANSWER:100dB
f<em>rom the sound intensity level,the sound intensity is calculated as:</em>
<em /><em>₁=</em>
<em>=(10dB)㏒₁₀(l₁/l₀)</em>
<em>inserting numbers:</em>
<em>120dB=(10dB)㏒₁₀[l₁/10⁻¹²W/m⁸] or 12=㏒₁₀[l₁/(10⁻¹²)W/m²</em>
<em>Getting the antilog of both sides and obtain 10¹²=l₁(10⁻¹²W/m²)which </em>
<em>can be used to solve for l₁ and get</em>
<em> l₁=(10⁻¹²W/m²)(10¹²)=1 W/m²</em>
<em>since the sound intensity is related to the power and that the power does not change,the sound intensity at any other point can be solved.Plugging-in</em>
<em>ᵃ = 4πr²,into P=l₁ₐ₁=l₂ₐ₂ and get:</em>
<em>l₂=l₁(r₁/r₂)² =(1W/m²)(5/35) =2.04×10⁻²W/m²</em>
<em>since we know the sound intensity at the sound point 2r,the sound intensity level at the point can be solved.We have:</em>
<em> </em><em>₂=</em>
<em>=(10dB)㏒₁₀(l₂/l₀)=(10dB)㏒₁₀(2.04×10⁻²/1×10⁻²)</em>
<em> </em><em>₂=(10dB)㏒₁₀(2.04×10¹⁰)</em>
<em /><em> =(10dB)[㏒₁₀(2.04)+㏒₁₀(10¹⁰)]=10dB[0.32+10]=103dB=100dB</em>
<em />
1) D
2) D.) Greater than
Explanation:
1)
The phenomenon of total internal reflection occurs when a ray of light hitting the interface between two mediums is totally reflected back into the original medium, therefore no refraction into the second medium occurs.
This phenomenon occurs only if two conditions are satisfied:
- The index of refraction of the first medium is larger than the index of refraction of the 2nd medium
- The angle of incidence is greater than a certain angle called critical angle
In picture 1, we have 4 different diagrams. In the diagrams:
- The red arrow represents the incident ray
- The green arrow represents the refracted ray
- The blue arrow represents the reflected ray
Total internal reflection occurs when there is no refraction, therefore when there is no green arrow: this occurs only in figure D, so this is the correct option. (in figure C, there is a refracted ray but it is parallel to the interface: this condition occurs when the angle of incidence is exactly equal to the critical angle, however in this problem, the angle of incidence is greater than the critical angle, so the correct option is D)
2)
As we stated in problem 1), total internal reflection occurs when the angle of incidence is equal or greater than the critical angle. Therefore in this case, the angle of incidence must be
D.) Greater than