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densk [106]
3 years ago
14

23) A high school website directs parents to not allow student access to blue laser pointers or allow the students to bring them

to school. It includes a video describing the danger inherent in the misuse of all laser pointers particularly the blue laser pointer. Why would they claim that blue laser pointers are more of a concern than red laser pointers?
Physics
1 answer:
vekshin13 years ago
6 0
Mainly because of the higher energy of blue light than red light.

In fact, light is made of photons, each one carrying an energy equal to
E=hf
where h is the Planck constant while f is the frequency of the light.
The frequency of red light is approximately 450 THz, while the frequency of blue light is about 650 Hz. Higher frequency means higher energy, so blue light is more energetic than red light and therefore it can cause more damages than red light.
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This force can either push the block upward at a constant velocity or allow it to slide downward at a constant velocity. The mag
Dmitry [639]

Answer:

Part a)

F = 135.7 N

Part b)

F = 62.5 N

Explanation:

Part a)

If block is sliding up then net force must be zero and friction will be in opposite to the direction of motion of the block

Fcos\theta = mg + F_f

Fsin\theta = F_n

so we have

Fcos\theta = mg + \mu(Fsin\theta)

F(cos\theta - \mu sin\theta) = mg

F = \frac{mg}{cos\theta - \mu sin\theta}

F = \frac{55}{cos50 - 0.310(sin50)}

F = 135.7 N

Part b)

If block is sliding down then net force must be zero and friction will be in opposite to the direction of motion of the block

Fcos\theta = mg - F_f

Fsin\theta = F_n

so we have

Fcos\theta = mg - \mu(Fsin\theta)

F(cos\theta + \mu sin\theta) = mg

F = \frac{mg}{cos\theta + \mu sin\theta}

F = \frac{55}{cos50 + 0.310(sin50)}

F = 62.5 N

6 0
3 years ago
What are the only elements that exist in nature as isolated atoms
agasfer [191]

Answer:

The only such elements are the Noble Gases (He, Ne, Ar, Kr, Xe, Rn)

(that is helium, neon, argon, krypton, xenon and radon)

Term: Monoatomic

Explanation:

6 0
3 years ago
Define any two characteristics of sound​
Oliga [24]

Answer:

five characteristics: Wavelength, Amplitude, Time-Period, Frequency and Velocity or Speed

5 0
3 years ago
A long solenoid with 1.65 103 turns per meter and radius 2.00 cm carries an oscillating current I = 6.00 sin 90πt, where I is in
Leno4ka [110]

Answer:

The  electric field  is 35\cos(90\pi t)\ mV/m

Explanation:

Given that,

Radius = 2.00 cm

Number of turns per unit length n= 1.65\times10^{3}

Current I = 6.00\sin 90\pi t

We need to calculate the induced emf

\epsilon =\mu_{0}nA\dfrac{dI}{dt}

Where, n = number of turns per unit length

A = area of cross section

\dfrac{dI}{dt}=rate of current

Formula of electric field is defined as,

E=\dfrac{\epsilon}{2\pi r}

Where, r = radius

Put the value of emf in equation (I)

E=\dfrac{\mu_{0}nA\dfrac{dI}{dt}}{2\pi r}....(II)

We need to calculate the rate of current

I=6.00\sin 90\pi t....(III)

On differentiating equation (III)

\dfrac{dI}{dt}=90\pi\times6.00\cos(90\pi t)

Now, put the value of rate of current in equation (II)

E=\dfrac{4\pi\times10^{-7}\times1.65\times10^{3}\times\pi\times(2.00\times10^{-2})^2\times90\pi\times6.00\cos(90\pi t)}{2\pi\times 2.00\times10^{-2}}

E=35\cos(90\pi t)\ mV/m

Hence, The  electric field  is 35\cos(90\pi t)\ mV/m

7 0
3 years ago
Read 2 more answers
The charge that passes a cross-sectional area A=10-4 m2 varies with time according
Anarel [89]

Answer:

Current = dQ/dt

or I = dQ/dt

Where I represents current.

Which is the rate of flow of charge.

Q=4 + 2t + t²

dQ/dt = 2 + 2t --- This is the relation that gives the instantaneous current.

At time t=2sec

dQ/dt = I = 2 + 2t

= 2 + 2(2)

=2 + 4

= 6A.

6 0
3 years ago
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