What happens when you sit in a chair?

Very short pulses of high-intensity laser beams are used to repair detached portions of the retina of the eye. The brief pulses

Tom [10]

Answer:

a) U = 0.375 mJ

b) p_rad = 4.08 mPa

c) λ_med = 604 nm ; f_med = 3.7 * 10^14 Hz

d) E_o = 3.04 * 10^4 V / m , B _o = 1.013 *10^-4 Nm/Amp

Explanation:

Given:

λ_air : wavelength = 810 * 10^(-9) m

P: Power delivered = 0.25 W

d : Diameter of circular spot = 0.00051 m

c : speed of light vacuum = 3 * 10^8 m/s

n_air : refraction Index of light in air = 1

n_med : refraction Index of light in medium = 1.34

ε_o : permittivity of free space = 8.85 * 10^-12 C / Vm

part a

The Energy delivered to retina per pulse given that laser pulses are 1.50 ms long:

U = P*t

U = (0.25 ) * (0.0015 )

U = 0.375 mJ

Answer : U = 0.375 mJ

part b

What average pressure would the pulse of the laser beam exert at normal incidence on a surface in air if the beam is fully absorbed?

p_rad = I / c

Where I : Intensity = P / A

p_rad = P / A*c

Where A : Area of circular spot = pi*d^2 / 4

p_rad = 4P / pi*d^2*c

p_rad = 4(0.25) / pi*0.00051^2*(3.0 * 10^8)

p_rad = 0.00408 Pa

Answer : p_rad = 4.08 mPa

part c

What are the wavelength and frequency of the laser light inside the vitreous humor of the eye?

λ_med = n_air*λ_air / n_med

λ_med = (1) * (810 nm) / 1.34

λ_med = 604 nm

f_med = f_air

f_med = c / λ_air

f_med = (3*10^8) / (810 * 10^-9)

f_med = 3.7 * 10^14 Hz

Answer : λ_med = 604 nm ; f_med = 3.7 * 10^14 Hz

d)

What is the electric and magnetic field amplitude in the laser beam?

I = P / A

I = 0.5*ε_o*c*E_o ^2

I = 4P / pi*d^2

Hence, E_o = ( 8 P / ε_o*c*pi*d^2 ) ^ 0.5

E_o = ( 8 * 0.25 / (8.85*10^-12) * (3*10^8) * π * (0.00051)^2) ^ 0.5

E_o = 3.04 * 10^4 V / m

For maximum magnetic field strength:

B_o = E_o / c

B_o = 3.04 * 10^4 / (3*10^8)

B _o = 1.013 *10^-4 Nm/Amp

Answer: E_o = 3.04 * 10^4 V / m , B _o = 1.013 *10^-4 Nm/Amp

5 0

3 years ago

What happens to the volume the gas occupies when the pressure on a gas increases?

taurus [48]

Each time they collide with the walls they exert a force on them. More collisions mean more force, so the pressure will increase. When the volume decreases, the pressure increases. This shows that the pressure of a gas is inversely proportional to its volume.

8 0

3 years ago

Read 2 more answers

PRACTIC

klasskru [66]

Answer:

2482 Kg.m/s

Explanation:

Momentum is a product of mass of an object and its velocity with consideration to the direction of velocity and expressed as, p=mv where m represent mass of the ostrich and v is the velocity in m/s, p is momentum.

Substituting the mass of ostrich with 146 kg and the velocity as 17 m/s then the momentum of the ostrich is equal to

P=146*17=2482 kg.m/s

Therefore, the momentum of ostrich is equal to 2482 kg.m/s

6 0

4 years ago

Current always returns to the:

Arlecino [84]

Current always returns to the negative terminal.

<u>Explanation</u>:

Current flows from a positive to a negative terminal. It is due to the flow of negative electrons to positive side. The current flows from a high potential to a low potential. There is high concentration of electrons at the positive terminal and low concentration at the negative terminal. When the circuit is complete the electrons move from a high concentration to low concentration i.e; from positive terminal to negative terminal.

8 0

4 years ago

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A terrorist throws a grenade with a 6.00 second fuse off a building 150.0 m high at a speed of 10.0 m/s. If the angle at which t

igomit [66]

Here we have a projectile motion. It is type of motion that is made of a vertical shot and a horizontal shot. This is how we will solve it.

Firste step is to find horizontal and vertical component of a speed.
$v_{0x} =v_{0} * cos \alpha$ \\ v_{0y} = v_{0} * sin \alpha [/tex]

We are given this information:
$v_{0} = 10 m/s \\ h=150m \\ \alpha =-30°$
Angle is negative because it is below the horizontal.

VERTICAL SHOT
Time needed for a grenade to fall to the bottom of a building is given by a formula:
$t= \frac{ v_{0y} }{g} \\ t= \frac{v_{0} * sin \alpha}{g} \\ t= \frac{-10*sin(-30)}{9.81} \\ t=0.51s$
We used negative value for a speed because it is considered that upwards shot has positive value and downwards shot has negative value.

The grenade will not explode before it hits the ground.

HORIZONTAL SHOT
<span>The horizontal distance from the building at which the grenade will land is called range. The formula for a range is given by:
</span> $R= v_{0x} * \sqrt{ \frac{2h}{g} } \\ R=v_{0} * cos \alpha* \sqrt{ \frac{2h}{g} } \\ R=10*cos(-30)* \sqrt{ \frac{2*150}{9.81} } \\ R=47.89m$

The grenade will hit the ground at distance of 47.89m.

7 0

3 years ago