A quantum dot may be modeled as an electron in a spherical well with perfectly reflecting walls. Design a quantum dot whose characteristic frequency of emission is 10 GHz, where characteristic frequency corresponds to decay from the first excited state to the ground state. In other words, obtain the radius a of the spherical cavity that has this property

Answer:

thank you

Explanation:

Answer:

273.15

Explanation:(32°F − 32) × 5/9 + 273.15 = 273.15K

Answer:

3.3*10^-28j

Explanation:

A P E X

The energy of an electromagnetic wave that has a frequency of 5.0 * 10^5 Hz is 3.3 * 10 ^ -28 J

Electromagnetic waves are the waves that are created as a result of vibration between an electric field and  a magnetic field . They are composed of oscillating magnetic and electric field

Energy of Electromagnetic waves can be calculated by

Energy = h * f             where  h = plank's constant = 6.626 * 10^-34 J s.

                                                f = frequency of electromagnetic waves  

given :  h =  6.626 * 10^-34 J s.

            frequency =  5.0 * 10^5 Hz  

Energy  of  electromagnetic waves = (6.626 * 10^-34 J s)  *( 5.0 * 10^5 Hz)

                        = 33.13 * 10 ^ -29 J

                        = 3.3 * 10 ^ -28 J

correct answer is c)3.3 * 10 ^ -28 J

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Explanation:

Given that,

Mass of the particle, m = 4 kg

Speed of the particle, v = 2.5 m/s

The radius of the circle, r = 2 m

We need to find the angular momentum about the center of the circle. The formula for the angular momentum is given by :

[tex]L=mvr[/tex]

Substitute all the values,

[tex]L=4\times 2.5\times 2\\\\L=20\ kg{\cdot}m^2s[/tex]

So, the angular momentum of the particle is 20 kg-m² s.

Answer:

θ = 22.2

Explanation:

This is a diffraction exercise

        a sin θ = m λ

The extension of the third zero is requested (m = 3)

They indicate the wavelength  λ = 630 nm = 630 10⁻⁹ m and the width of the slit  a = 5 10⁻⁶ m

         sin  θ = m λ / a

         sin  θ = 3 630 10⁻⁹ / 5 10⁻⁶

         sin  θ = 3.78 10⁻¹ = 0.378

          θ = sin⁻¹  0.378

to better see the result let's find the angle in radians

          θ = 0.3876 rad

let's reduce to degrees

         θ = 0.3876 rad (180º /π rad)

         θ = 22.2º

Answer:

.

Kirchhoff's circuit laws are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits. They were first described in 1845 by German physicist Gustav Kirchhoff.[1] This generalized the work of Georg Ohm and preceded the work of James Clerk Maxwell. Widely used in electrical engineering, they are also called Kirchhoff's rules or simply Kirchhoff's laws. These laws can be applied in time and frequency domains and form the basis for network analysis.

Both of Kirchhoff's laws can be understood as corollaries of Maxwell's equations in the low-frequency limit. They are accurate for DC circuits, and for AC circuits at frequencies where the wavelengths of electromagnetic radiation are very large compared to the circuits.

Answer:The different types of radiation are defined by the the amount of energy found in the photons. Radio waves have photons with low energies, microwave photons have a little more energy than radio waves, infrared photons have still more, then visible, ultraviolet, X-rays, and, the most energetic of all, gamma-rays.

Explanation:

Answer:

Energy: The ability to do work

Kinetic energy: Kinetic energy is the energy an object has due to its motion

Potential energy: potential energy is the energy that is stored in an object

Work: Work is the transfer of energy by a force acting on an object as it is displaced

Friction: Friction acts as a resisting force which is generated , when two solid surfaces slide against one another

Answer:

a) P = 118.4 W,  b) t = 7.9 10⁻⁵ s

Explanation:

a) Let's analyze this interesting exercise a bit, we suppose that all the laser

energy is used to heat the aluminum, we should calculate the energy necessary to bring the solid aluminum to the melting temperature and add the energy to carry out the change of solid state to liquid,  

let's use the calorimeter equation  

Q₁ = m c_e ΔT

and the energy of change of these solid to liquid (fusion process)  

Q₂ = m L  

the energy required to create the hole is  

Q_ {total} = Q₁ + Q₂  

if there are no losses this is the laser energy  

E = Q_ {total}

The aluminun data c_e =9000 J/kgC, L = 322 103 J/kg, ρ = 2.7 103 kg/m3 , T₂ = 660C, T₀= 25C

Let's find the mass of the hole, which we approximate by a cylinder of diameter d = 0.25 mm = 0.25 10⁻³ m and a thickness of e = 1 mm = 1 10⁻³ m  

let's use the concept of density  

ρ = m / V

the volume of a cylinder is  

V = π r² e = π (d²/4)  e  

we substitute  

m = [tex]\rho \pi \frac{d^2 e}{4}[/tex]

let's calculate  

m = π/4  2.7 10³ (0.25 10⁻³)²  1 10⁻³  

m = 1,325 10⁻⁷ kg

we calculate the energy  

E = 1,325 10⁻⁷  900 (660 - 25) + 1,325 10⁻⁷ 322 10³  

E = 7.57 10⁻² + ​​4.27 10⁻²  

E = 1.184 10⁻¹ J

Let's use the power ratio  

P = E / t  

P = 0.1184 /1 10⁻³  

P = 118.4 W

b) In this part they indicate that the laser power is P = 1500 W, find the time to deposit the energy to melt the aluminum  

P = E / t  

t = E / P  

t = 0.1184 / 1500  

t = 7.9 10⁻⁵ s

according to it's nature

The motion of an apple when it falls from a tree is

b) Accelerating

The motion of apple is when it falls from a tree is the case of free fall.

During free fall , the initial velocity of the apple or any object is zero but it gains some velocity due to gravitatonal acceleration .

Answer:

Block of aluminum

Explanation:

The block of aluminum because of the conductivity, and is a metal, so it gets hotter faster

The temperature of wood and the aluminium will depend upon thier thermal coductivity.

The thermal conductivity of any material is defined as the amount of heat from a material can flow in a unit area per unit degree centigrade for a unit distance.

The thermal conductivity of wood is around 0.90 to 0.197 w/mk and that of aluminium is around 88 to 251 w/mk.

We can see that the aluminium block will absorb much amount of heat as compared to the wood block. Because the thermal conductivity of aluminium is much higher then the wood.

Hence temperature of wood and the aluminium will depend upon thier thermal coductivity.

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Answer:

Vernier calipers is used to measure the internal diameter of a beaker

Answer:

[tex]6.28\times 10^{-5}\ \text{T}[/tex]

[tex]1.92\times 10^{-6}\ \text{Nm}[/tex]

Explanation:

[tex]\mu_0[/tex] = Vacuum permeability = [tex]4\pi 10^{-7}\ \text{H/m}[/tex]

[tex]I_l[/tex] = Current in circular loop = 13 A

[tex]r_l[/tex] = Radius of circular loop = 13 cm

[tex]N[/tex] = Number of turns = 58

[tex]r_c[/tex] = Radius of coil = 0.94 cm

[tex]I_c[/tex] = Current in coil = 1.9 A

[tex]\theta[/tex] = Angle between loop and coil = [tex]90^{\circ}[/tex]

Magnitude of magnetic field in circular loop

[tex]B_l=\dfrac{\mu_0I_l}{2r_l}\\\Rightarrow B_l=\dfrac{4\pi 10^{-7}\times 13}{2\times 13\times 10^{-2}}\\\Rightarrow B_l=6.28\times 10^{-5}\ \text{T}[/tex]

The magnetic field produced by the loop at its center is [tex]6.28\times 10^{-5}\ \text{T}[/tex].

Torque is given by

[tex]\tau=\pi NI_cr_c^2B_l\sin\theta\\\Rightarrow \tau=\pi 58\times 1.9\times (0.94\times 10^{-2})^2\times 6.28\times 10^{-5}\sin90^{\circ}\\\Rightarrow \tau=1.92\times 10^{-6}\ \text{Nm}[/tex]

The torque on the coil due to the loop [tex]1.92\times 10^{-6}\ \text{Nm}[/tex].

Answer:

gravity wave

Explanation:

Answer:

A. Trial and error

Explanation:

Trial and error method is a method adopted when trying to solve a quadratic equation. This equation is mostly the balancing of the right hand side and the left hand side in-order to form a unique point or to equate to zero when one is subtracted from the other. In trail and error method, the coefficients is used to determine when the actual equation is balanced and the likely answer it should be if the equation is expanded through multiplication method.

Answer:

Precision is determined by a statistical method called a standard deviation To determine if a value is precise find the average of your data, then subtract each measurement from it

Answer:

Option b ( It is a closed system) is the appropriate answer.

Explanation:

The other options are not linked to the situation in question. Thus, the answer is correct.

Answer:

Compression, decrease in volume of any object or substance resulting from applied stress. Compression may be undergone by solids, liquids, and gases and by living systems.

Explanation:

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Answer:

v = 2099.5 km/h, v' =  -618.8 km/h

or

v =-1996.6 km/h, v' = 721.7 km/h

Explanation:

From the law of conservation of momentum,

Total momentum before collision = Total momentum after collision

For elastic,

mu+m'u' = mv+m'v'..................... Equation 1

Total kinetic energy before collision is equal to total kinetic energy after collision

mu²+m'u'² = mv²+m'v'²............. Equation 2

Where m and m' are the mass of the car and truck respectively, and u and u' are the initial velocity of the car and the truck respectively, v and v' are the final velocity of the car and the truck respectively.

Given: m = 1800000 g = 1800 kg, m' = 5500 kg, u = 150 km/h, u' = 100000 km/h

Substitute these values into equation 1 and 2

1800(150)+5500(100000) = 1800v+5500v'

1800v+5500v' = 375500................... Equation 3

1800(150²) +5500(100000²) = 1800v²+5500v'²...................... Equation 4

Solving equation 3 and 4 simultaneously,

v = 2099.5 km/h, v' =  -618.8 km/h

or

v =-1996.6 km/h, v' = 721.7 km/h

Answer:

1 gm = 1000 mg

N = No e^-y t       where y = lambda the decay constant

N / N0 = .9969

ln .9969 = - y t

-.00310 = - 5 y

y = .00310 / 5 = .000621

So the half-life = .693 / y

T^1/2 = .693 / .000621 = 1116 or about 1120 yrs

Answer:

a) 34.17J/m^3

b) 0.0468 J

Explanation:

a) Calculate the energy density of the magnetic field inside the solenoid as follows:

[tex]u_{B} &=\frac{U}{A l} \\ &=\frac{L I^{2}}{2 A l} \quad\left(U=\frac{1}{2} L I^{2}\right) \\ &=\frac{\mu_{0} N^{2} A I^{2}}{2 A l^{2}} \quad\left(L=\frac{\mu_{0} N^{2} A}{l}\right) \\ &=\frac{\mu_{0} N^{2} I^{2}}{2 l^{2}}[/tex]

Substitute the corresponding values in the above equation.

[tex]u_{B} &=\frac{4 \pi\left(10^{-7}\right)(1260)^{2}(8.78)^{2}}{2(0.693)^{2}} \\

&=34.17 \mathrm{~J} / \mathrm{m}^{3}[/tex]

b) Calculate the total energy stored in the solenoid as follows:

[tex]U &=u_{B} A l \\ &=(34.17)\left(24 \times 10^{-4}\right)\left(69.3 \times 10^{-2}\right) \\ &=0.0468 \mathrm{~J}[/tex]

Answer:

(1/2)*n = .05      by the definition of half-life where n is the number of half-lives

n ln .5 = ln .05

n = ln .05 / ln .5 = 4.32   number of half-lives

So 4.32 * 20 = 86.4 years    has passed

Actually, they only want the mass left. However, all that has changed is that

95% of the original radioactive atoms have changed to a different form of about the same amount of mass. The amount of mass remaining would be about the same. Also, one doesn't know the percentage of radioactive atoms

that formed the original mass.

Explanation:

The least count of the normal scale is 1mm whereas the least count of vernier calliper is 0.01 mm

Answer:

     P₁ = ⅔ P₀

Explanation:

For this exercise we can use the ideal gas equation

         PV = n R T

let's write the equation for the initial point, where we will use the subscript o and the end with subscript 2

Suppose the temperature does not change in the process

        P₀V₀ / n₀ = P₁V₁ / n₁

They tell us that

      V₁ = V₀ / 2

       n₁ = n₀ / 3

we substitute

     [tex]P_o \frac{V_o}{n_o} = P_1 \frac{V_o}{2} \frac{3}{n_o}[/tex]  

        P₀ = [tex]\frac{3}{2}[/tex]     P₁  

        P₁ = ⅔ P₀

Answer:

The gunner must apply 240 N  to the gun to stop it from moving back.

Explanation:

Answer:

1)   λ = 24.7 cm,  2) f = 13.88 Hz, 3)  L = 117.3 cm

Explanation:

1) This is a resonance process, that is, the wave going downwards will interfere with the wave going upwards.

This is a tube with one end closed and the other open, at the closed end there is a node and at the open end a belly, so the resonances are

       L = λ / 4

       λ = 4L                     1st harmonic

       λ = 4L / 3                third harmonic

       λ = 4L / 5                fifth harmonic

       λ = 4L / n ’              n’ odd number   n ’= (2n +1)

the wavelength is requested for the eighth resonance n = 8, the corresponding prime number is

          n ’= 2 8 +1

          n ’= 17

we substitute

     λ = 4 105/17

     λ = 24.7 cm

2) the speed of the wave is related to the wavelength and frequency

          v =   λf

          f = v /λ

          f = 343 / 24.7

          f = 13.88 Hz

3) the next resonance occurs for n = 9, so the prime number is

         n ’= 2 9 +1

         n ’= 19

         L = n’ λ / 4

         L = 19 λ / 4  

We must suppose a value for the wavelength, if the wavelength is present in the tube and the length of the column increases, the resonance number increases

         L = 19 24.7/4

         L = 117.3 cm