Answer: Δβ (dB) = -13.1dB
Explanation:
The intensity of sound is inversely proportional to the square of the distance between them.
I ∝ 1/r²
I₁/I₂= r₂²/r₁² .....1
When the listener increases his distance from the source by a factor of 4.49.
Then,
r₂/r₁= 4.49
From equation 1
I₁/I₂ = (4.49)²
I₁/I₂ = 20.16
I₂/I₁ = 1/20.16
The change in sound intensity in dB can be given as
Δβ (dB) = 10 log(I₂/l₁) = 10log(1/20.6) = -13.1dB
The human eye is one of the most valuable sense organ. The closest object that a typical young person with normal vision can focus closest to is 25 cm
The lens in the eye forms the image on the retina. The image formed is real and inverted. The retina is a very delicate membrane containing numerous light sensitive cells.
This light sensitive cells gets activated when light falls on it and generates electric signals. These electric signals are sent to the brain via the optic nerves present in the eye. The brain finally processes these signals and thus we see the object clearly.
The ability of the lens of the eye to adjust its focal length accordingly is called the power of accommodation,
The minimum distance, at which the object can be seen clearly without any strain is called the least distance of distinct vision.
To see an object clearly without any strain is when we place it at about 25 cm from the eye.
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Answer:
The word Allopatric is derived from the Greek words allos = other and Patris = fatherland. Allopatric specification happens when the biological population of the same specie got separated from one another such that it stopped their gene flow or gene migration. It happens due to the geographical changes such as the movement of continents, changes in glaciers, mountains or oceans and it could be happened because of human activities like agriculture and industrial development etc. The first step of Allopatric specification is Geographical isolation. The species got separated and the long distances makes them unable to interbreed.
