Answer:
a differenceis that the string needs force to be used. without something pulling on it then it wont make the noise. meanwhile the pipe only needs air to be blow Wich can be caused naturally or intentionally
Answer:
a) 
s
b) 3.41 mm
Explanation:
a)
We take the speed of light, c = 
m/s and the refractive index of glass as 1.517.
Speed = distance/time
Time = distance/speed
Refractive index, n = speed of light in vacuum / speed of light in medium
b)
We take the refractive index of water as 1.333.
Speed in water = speed in vacuum / refractive index of water
Distance = speed * time
d = 3.41 mm
Set up a proportion
1 mile/1.6 km = 20,000miles/x
Cross Multiply
x = (20,000) * (1.6)
x = 32,000 kilometers
The efficiency of a light source is the percentage of its energy input that gets radiated as visible light if some of the blue light in an led is used to cause a fluorescent material to glow the overall efficiency of the LED decreases.
How efficient is LED?
Different wavelengths that correlate to different visible colours are used in LED light therapy. Various shades pierce the skin at different rates.
- Your skin's outermost layer is impacted by blue light.
- Yellow light is more enveloping.
- Red light penetrates your skin more deeply.
- The deepest penetrating light is near-infrared.
Different LED hues have various effects. For instance, according to experts red LED light therapy has the potential to reduce inflammation and boost collagen formation, which declines with age and is crucial for maintaining youthful-looking skin.
Acne-causing bacteria may be destroyed by a blue LED light therapy (P. acnes).
Hence the answer is the overall efficiency of the LED decreases.
Learn more about wavelength here,
brainly.com/question/1263539
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