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melomori [17]
2 years ago
8

3. Nearsighted people can undergo a medical procedure called keratotomy to produce normal (or at least more-normal) vision. In t

his procedure the shape of the cornea (and thus its refractive power) is changed, usually by the removal of tissue by the action of an excimer laser. If a nearsighted person has a far point 50 cm from the eye, by how much and in what direction (i.e., increase or decrease) must the refractive power of the cornea be changed in order to restore normal vision (i.e. far point at least 6 m from the eye)?
Physics
1 answer:
Mademuasel [1]2 years ago
7 0

Answer:

P= -1.83D

Explanation:

Given,

u=-6 m

v=-50 cm = - 0.5 m

the power of the lens

P = 1/f = 1/v = 1/u

P = 1/ -0.50 + 1/6

P = -1.83D

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4.A photon of green light strikes an unknown metal and an electron is emitted. The voltage is set to 2 volts. The electron canno
Anarel [89]
4) The correct answer is:
<span>B. An electron will be emitted in the second experiment, but it cannot be determined whether it will reach the second plate. 

In fact, violet light has higher frequency than green light. This means that photons of violet light carry more energy than photons of green light (remember that the energy of a photon is proportional to its frequency: </span>E=hf)<span>, so when they hit the surface of the metal, more energy is transferred to the electrons. The electron was already emitted with green light, so it must be emitted also with violet light, given the more energy transferred. The electron will also have more kinetic energy when hit by violet light, however, we cannot determine if it will reach the second plate, since we don't know how much energy has been used to extract the electron from the metal (in fact, we don't know the work function of the metal, i.e. the energy needed to extract the electron)


3)  The correct answer is
</span><span>A. Violet light will cause electrons to be emitted at greater velocities than those removed by green light.

In fact, </span>violet light has higher frequency than green light. This means that photons of violet light carry more energy than photons of green light (remember that the energy of a photon is proportional to its frequency: E=hf), so when they hit the surface of the metal, more energy is transferred to the electrons. Therefore, the emitted electrons will have on average greater energy (and so, greater velocity) than those removed by green light.
3 0
2 years ago
g The international space station has an orbital period of 93 minutes at an altitude (above Earth's surface) of 410 km. A geosyn
krok68 [10]

Answer:

r = 4.21 10⁷ m

Explanation:

Kepler's third law It is an application of Newton's second law where the forces of the gravitational force, obtaining

            T² = (\frac{4\pi }{G M_s} ) r³             (1)

           

in this case the period of the season is

            T₁ = 93 min (60 s / 1 min) = 5580 s

            r₁ = 410 + 6370 = 6780 km

            r₁ = 6.780 10⁶ m

for the satellite

           T₂ = 24 h (3600 s / 1h) = 86 400 s

if we substitute in equation 1

            T² = K r³

            K = T₁²/r₁³

            K = \frac{ 5580^2}{ (6.780 10^6)^2}

            K = 9.99 10⁻¹⁴ s² / m³

we can replace the satellite values

            r³ = T² / K

            r³ = 86400² / 9.99 10⁻¹⁴

            r = ∛(7.4724 10²²)

            r = 4.21 10⁷ m

this distance is from the center of the earth

7 0
2 years ago
Go to the roller coaster simulation and click on the "launch" button. Pay attention to the pie chart as the roller coaster moves
Paladinen [302]

Answer:

The kinetic energy INCREASES as the roller coaster goes downhill.

Kinetic energy is greatest at POINT 2

Potential energy is greatest at POINT 1

Kinetic energy is decreasing while potential energy is increasing between points 3 AND 4

Which chart comes closest to the relationship between kinetic energy and potential energy at point 6 - CHART OF ANY POINT IN THE SAME HEIGHT AS OF 6

Explanation:

⇒As the potential energy increases , kinetic energy decreases.

⇒Potential energy here is gravitational potential energy.

⇒Thus, more we move away from the centre of the earth , more will be the gravitational potential energy or decrease in kinetic energy

3 0
2 years ago
Read 2 more answers
A 70kg man runs at a pace of 4 m/s and a 50g meteor travels at 2 km/s. Which has the most kinetic energy?.
kirill115 [55]

Answer:

the 70kg man

Explanation:

because he has more weight and is moving faster

4 0
2 years ago
Use the momentum equation for photons found in this week's notes, the wavelength you found in #3, and Plank’s constant (6.63E-34
Nostrana [21]
To help you I need to assume a wavelength and then calculate the momentum.

The momentum equation for photons is:

p = h / λ , this is the division of Plank's constant by the wavelength.

Assuming λ = 656 nm = 656 * 10 ^ - 9 m, which is the wavelength calcuated in a previous problem, you get:

p = (6.63 * 10 ^-34 ) / (656 * 10 ^ -9) kg * m/s

p = 1.01067 * 10^ - 27 kg*m/s which  must be rounded to three significant figures.

With that, p = 1.01 * 10 ^ -27 kg*m/s

The answers are rounded to only 2 significan figures, so our number rounded to 2 significan figures is 1.0 * 10 ^ - 27 kg*m/s

So, assuming the wavelength λ = 656 nm, the answer is the first option: 1.0*10^-27 kg*m/s.
7 0
2 years ago
Read 2 more answers
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