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4 years ago

Which scientist proposed the idea of a sun-centered solar system instead of an earth-centered solar system?

1 answer:

5 0

Nicolaus Copernicus

This theory was first proposed by Nicolaus Copernicus. Copernicus was a Polish astronomer. He first published the heliocentric system in his book: De revolutionibus orbium coelestium, "On the revolutions of the heavenly bodies," which appeared in 1543.

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An ideal photo-diode of unit quantum efficiency, at room temperature, is illuminated with 8 mW of radiation at 0.65 µm wavelengt

nadya68 [22]

Answer:

I = 4.189 mA V = 0.338 V

Explanation:

In order to do this, we need to apply the following expression:

I = Is[exp^(qV/kT) - 1] (1)

However, as the junction of the diode is illuminated, the above expression changes to:

I = Iopt + Is[exp^(qV/kT) - 1] (2)

Now, as the shunt resistance becomes infinite while the current becomes zero, we can say that the leakage current is small, and so:

I ≅ Iopt

Therefore:

I ≅ I₀Aλq / hc (3)

Where:

I₀A = Area of diode (radiation)

λ: wavelength

q: electron charge (1.6x10⁻¹⁹ C)

h: Planck constant (6.62x10⁻³⁴ m² kg/s)

c: speed of light (3x10⁸ m/s)

Replacing all these values, we can get the current:

I = (8x10⁻³) * (0.65x10⁻⁶) * (1.6x10⁻¹⁹) / (6.62x10⁻³⁴) * (3x10⁸)

I = 4.189x10⁻³ A or 4.189 mA

Now that we have the current, we just need to replace this value into the expression (2) and solve for the voltage:

I = Is[exp^(qV/kT) - 1]

k: boltzman constant (1.38x10⁻²³ J/K)

4.189x10⁻³ = 9x10⁻⁹ [exp(1.6x10⁻¹⁹ V / 1.38x10⁻²³ * 300) - 1]

4.189x10⁻³ / 9x10⁻⁹ = [exp(38.65V) - 1]

465,444.44 + 1 = exp(38.65V)

ln(465,445.44) = 38.65V

13.0508 = 38.65V

V = 0.338 V

6 0

4 years ago

A ship is travelling due east at 30 km/hr and a boy runs across the deck

dsp73

Answer:

Vr = 20 [km/h]

Explanation:

In order to solve this problem, we have to add the relative velocities. We must remember that velocity is a vector, therefore it has magnitude and direction. We will take the sea as the reference measurement level.

Let's take the direction of the ship as positive. Therefore the boy moves in the opposite direction (Negative) to the reference level (the sea).

$V_{r}=30-10\\V_{r}=20 [km/h]$

8 0

3 years ago

What happens to centripetal acceleration as the radius of curvature decreases and the speed is constant, and why

lutik1710 [3]

It increases, because the centripetal acceleration is inversely proportional to the radius of the curvature.

Hopr it helps :)

4 0

3 years ago

The width of the central maxima, formed from light of wavelength 575 nm behind a single slit that has a width of 115 μm, is 1.15

Lady bird [3.3K]

Answer:

L = 1.15 m

Explanation:

The diffraction phenomenon is described by the equation

a sin θ = m λ

Where a is the width of the slit, λ the wavelength and m is an integer, the order of diffraction is left.

The diffraction measurements are made on a screen that is far from the slit, and the angles in the experiment are very small, let's use trigonometry

tan θ = y / L

tan θ = sint θ / cos θ≈ sin θ

We substitute in the first equation

a (y / L) = m λ

The first maximum occurs for m = 1

The distance is measured from the center point of maximum, which coincides with the center of the slit, in this case the distance is the total width of the central maximum, so the distance (y) measured from the center is

y = 1.15 / 2 = 0.575 cm

y = 0.575 10⁻² m

Let's clear the distance to the screen (L)

L = a y / λ

Let's calculate

L = 115 10⁻⁶ 0.575 10⁻² / 575 10⁻⁹

L = 1.15 m

3 0

3 years ago

How could you dissolve more solid solute in a saturated solution in a liquid solvent

tankabanditka [31]

If you saturated the solid it will turn into liquid and soon become an air

3 0

3 years ago