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3 years ago

How does the eye control the amount of light entering it?

Physics

2 answers:

Pani-rosa [81]3 years ago

7 0

Answer:

the retina of the eye contains photoreceptor cells that detect the light intensity, whether it is dim or bright, changing shape of iris.

Explanation:

in dim light, the receptors detect the light intensity, and in order to allow us to see more clearly, the radial muscles in iris contract, making the pupil widen(dilate), so more light enters eye.

in case of bright light, he receptors detect the light intensity, and in order to allow us to see more clearly, the circular muscles in iris contract, making the pupil narrow(constrict), so less light enters eye

Trava [24]3 years ago

3 0

Answer:

Dilating the pupils.

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3 years ago

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COMPLETE QUESTION:

When the magnetic flux through a single loop of wire increases by 30 Tm^2 , an average current of 40 A is induced in the wire. Assuming that the wire has a resistance of 2.5 ohms , (a) over what period of time did the flux increase? (b) If the current had been only 20 A, how long would the flux increase have taken?

Answer:

(a). The time period is 0.3s.

(b). The time period is 0.6s.

Explanation:

Faraday's law says that for one loop of wire the emf $\varepsilon$ is

$(1). \: \: \varepsilon = \dfrac{\Delta \Phi_B}{\Delta t }$

and since from Ohm's law

$\varepsilon = IR$ ,

then equation (1) becomes

$(2). \: \:IR= \dfrac{\Delta \Phi_B}{\Delta t }.$

(a).

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$(40A)(2.5\Omega)= \dfrac{30Tm^2}{\Delta t },$

which we solve for $\Delta t$ to get:

$\Delta t = \dfrac{30Tm^2}{(40A)(2.5\Omega)},$

$\boxed{\Delta t = 0.3s}$ ,

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(b).

Now, if the current had been $I =20A$ , then equation (2) would give

$(20A)(2.5\Omega)= \dfrac{30Tm^2}{\Delta t },$

$\Delta t = \dfrac{30Tm^2}{(20A)(2.5\Omega)},$

$\boxed{\Delta t = 0.6 s\\}$

which is a longer time interval than what we got in part a, which is understandable because in part a the rate of change of flux $\dfrac{\Delta \Phi_B}{\Delta t}$ is greater than in part b, and therefore , the current in (a) is greater than in (b).

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Explanation:

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3 years ago

if mass of an object is decreased to half and acting force is reduced by quarter the acceleration of its motion

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Answer:

See explanations below

Explanation:

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Divide both expressions

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3 years ago

How does the eye control the amount of light entering it?​

How does the eye control the amount of light entering it?