# Confused

### I need some help with this problem.?

I'm trying to work it, but I don't know if I have everything to solve this problem with. I got Power ( I think, .573), now where do i go with this problem?

A laser emits 1.48 x 10e18 photons per second in a beam of light that has a diameter of 1.96 mm and a wavelength of 513.0 nm. Determine each of the following for the electromagnetic wave that constitutes the beam.

(a) the average electric field strength

N/C

(b) the average magnetic field strength

T

1 AnswerPhysics1 decade ago### The photoelectric effect?

I know that hf - Wo = KE, but I'm unsure how to incorporate velocity into this equation.

Light is incident on the surface of metallic sodium, whose work function is 2.3 eV. The maximum speed of the photoelectrons emitted by the surface is 1.1 106 m/s. What is the wavelength of the light?

4 AnswersPhysics1 decade ago### Interference and the wave nature of light?

A slit whose width is 4.30 10e-5 m is located 1.32 m from a flat screen. Light shines through the slit and falls on the screen. Find the width of the central fringe of the diffraction pattern when the wavelength of the light is 640 nm.

Okay, I know the formulas such as sin(theta) = m(lambda) / width and lambda/width = Diffraction. However, I'm not entirely sure how to find the width of the central bright fringe.

2 AnswersPhysics1 decade ago### farsightedness and nearsightedness?

For this problem I know do (object distance) equals 23.3 cm and object height equals .23 cm. Now, I believe I'm supposed to find image height but I don't think I have enough information. What am I missing? Or do I have something wrong?

A person holds a book 25 cm in front of the effective lens of her eye; the print in the book is 2.3 mm high. If the effective lens of the eye is located 1.7 cm from the retina, what is the size (including the sign) of the print image on the retina?

2 AnswersPhysics1 decade ago### Converging and Diverging lenses?

I got half of this problem correct so far

. A diverging lens (f = -10 cm) is located 20.0 cm to the left of a converging lens (f = 31.5 cm). A 3.00 cm tall object stands to the left of the diverging lens, exactly at its focal point.

(a) Determine the distance of the final image relative to the converging lens.

I got this answer correct, -121.15 cm

(b) What is the height of the final image (including proper algebraic sign)? in cm

I know that hi/ho = -di/do but I'm not getting the correct answer. Any help will be appreciated.

1 AnswerPhysics1 decade ago### The electromagnetic spectrum?

Magnetic resonance imaging, or MRI, and positron emission tomography, or PET scanning, are two medical diagnostic techniques. Both employ electromagnetic waves. For these waves, find the ratio of the MRI wavelength (frequency = 6.42 x 10e7 Hz) to the PET scanning wavelength (frequency = 1.23 x 10e20 Hz).

I believe I use the equation c = f(wavelength) but I'm not sure how to incorporate these numbers into the equation.

2 AnswersPhysics1 decade ago### Need help working this problem?

This to me is a confusing chapter in Physics... I have the formulas, but I do not know what to use, if I need to set anything equal to, etc. Any help would be appreciated.

A circular loop of wire and a long, straight wire carry currents of I1 and I2 (see the drawing), where I2 = 6.1(I1). The loop and the straight wire lie in the same plane. The net magnetic field at the center of the loop is zero. Find the distance H, expressing your answer in terms of R, the radius of the loop.

http://i21.photobucket.com/albums/b272/Cajunboiler...

There is this same problem in my physics book that says I2 = 6.6(I1). and the answer is "H = 2.1 R" Any help would be appreciated in determining how to set up/work this problem.

1 AnswerPhysics1 decade ago### Motion of a charged particle in electric and magnetic fields?

A magnetic field has a magnitude of 1.2 10e-3 T, and an electric field has a magnitude of 5.7 10e3 N/C. Both fields point in the same direction. A positive 1.8 µC charge moves at a speed of 2.9 10e6 m/s in a direction that is perpendicular to both fields. Determine the magnitude of the net force that acts on the charge.

Now, wouldn't I add the force of the magnetic and electric fields together to get the answer? I came up with .0183 but my homework site is telling me I'm wrong.

3 AnswersPhysics1 decade ago### Wires, Resistors, voltages, etc.?

For the circuit shown in the drawing, find the current I through the R1 = 2.30 resistor and the voltage V of the battery to the left of this resistor if R2 = 7.00 .

http://i21.photobucket.com/albums/b272/Cajunboiler...

Please help me with this problem.

1 AnswerPhysics1 decade ago### Wires, Resistors, voltages and all that good stuff?

For the circuit shown in the drawing, find the current I through the R1 = 2.30 resistor and the voltage V of the battery to the left of this resistor if R2 = 7.00 .

http://i21.photobucket.com/albums/b272/Cajunboiler...

Now, I thought this was an easy problem.... but I'm having trouble coming up with the right answer. I think I might be overcomplicating it. If anyone could provide steps, I would greatly appreciate it.

1 AnswerPhysics1 decade ago### RC circuits?

In a heart pacemaker, a pulse is delivered to the heart 79 times per minute. The capacitor that controls this pulsing rate discharges through a resistance of 1.8 106 . One pulse is delivered every time the fully charged capacitor loses 64.3% of its original charge. What is the capacitance of the capacitor?

I have an equation that I believe I'm suppose to use Q = Qnot[ 1 - e^(-t/RC)] Wha numbers would I plug into this equation.

My best guess is .643Qnot[1 - e^ (-(60/79)/(1.8e6 x C)

Do I already know Q because that is confusing me.

2 AnswersPhysics1 decade ago### Can someone help me work this problem, kirchoff's rule?

Find the current in the 10.0 resistor in the drawing (V1 = 18.0 V and R1 = 18.0 ).

http://i21.photobucket.com/albums/b272/Cajunboiler...

I thought I knew how to do this. I used the loop rule, came up with a couple of equations. I tried to solve the current for the 10 ohm resistor, but none of the answers I've got are correct. I got 12.6, 7, and 1.1667. I thought would finally be the correct answer but it turns out I've been wrong 3 times. Can someone help me solve this equation?

1 AnswerPhysics1 decade ago### Kirchoff's Rules?

Find the magnitude and direction of the current in the 2.0 resistor in the drawing if R = 3.0 and V = 2.5 V.

http://i21.photobucket.com/albums/b272/Cajunboiler...

I know the direction is left. That's obvious. The thing that is confusing me about this problem is the extra voltage. I'm not sure what to do with it in helping me find the current. If there was only one, then I would definitely know how to do it.

2 AnswersPhysics1 decade ago### Series Wiring?

Okay, I thought I understood this but my homework site is telling me otherwise. What I did was add the total votage and came out with 40.12. I'm not sure if that is what I'm suppose to do or not for part (a).

Three resistors are connected in series across a battery. The value of each resistance and its maximum power rating are as follows: 5.0 and 20.5 W, 31.5 and 10.0 W, and 15.0 and 10.0 W.

(a) What is the greatest voltage that the battery can have without one of the resistors burning up?

V

(b) How much power does the battery deliver to the circuit in (a)?

W

If I know (a) then I should be able to do (b) by myself

4 AnswersPhysics1 decade ago### Physics problem question?

I'm trying to work this problem yet I cannot come up with a correct answer. Any help would be appreciated.

Two charges, -20 and +4.2 µC, are fixed in place on the x axis at x = 3.0 m and x = 0 m, respectively.

(a) At what spot along the x axis is the net electric field zero?

x = ? m

(b) What would be the force on a charge of +19 µC placed at this spot?

? N

3 AnswersPhysics1 decade ago### Physics, charges?

I'm not exactly sure where to start with this problem or which formula to use first. If you could provide some steps to solving this problem, it would be greatly appreciated.

A small plastic ball of mass 7.00 x 10^-3 kg and charge +0.150 µC is suspended from an insulating thread and hangs between the plates of a capacitor (see the drawing). The ball is in equilibrium, with the thread making an angle of 30.0° with respect to the vertical. The area of each plate is 0.0120 m2. What is the magnitude of the charge on each plate

1 AnswerPhysics1 decade ago### Electric field?

I got .314 for part A but I'm being told it's wrong. I know that the answer for part A has to be closer to 0 than 3. I know I need to set the Electric field to 0, but after that, I'm at a lost for what to plug in.

Two charges, -20 and +4.2 µC, are fixed in place on the x axis at x = 3.0 m and x = 0 m, respectively.

(a) At what spot along the x axis is the net electric field zero?

x = m

(b) What would be the force on a charge of +19 µC placed at this spot?

N

2 AnswersPhysics1 decade ago### Mass of protons, electrons?

I got 5.11e-14 for this answer, but it's wrong and I was wondering if someone could tell me how to work this problem.

Object A is metallic and electrically neutral. It is charged by induction so that it acquires a charge of -4.9 x 10^-6 C. Object B is identical to object A and is also electrically neutral. It is charged by induction so that it acquires a charge of +4.9 x 10^-6 C. Find the difference in mass between the charged objects.

in kg

1 AnswerPhysics1 decade ago### How do I work this problem with electrons and protons?

Yes, this seems like a very straightforward question.... I've tried it and got it wrong, but I'm not sure how to work it.

A metal sphere has a charge of +8.0 µC. What is the net charge after 7.0 x 10^13 electrons have been placed on it?

Ans in µC

1 AnswerPhysics1 decade ago### More Pressure and physics yay?

The Mariana trench is located in the Pacific Ocean at a depth of about 10700 m below the surface of the water. The density of seawater is 1025 kg/m3.

(a) If an underwater vehicle were to explore such a depth, what force would the water exert on the vehicle's observation window (radius = 0.15 m)?

in Newtons

(b) For comparison, determine the weight of a jetliner whose mass is 1.2 x 10^5 kg.

in Newtons

Yes, I am lost on this chapter. If anyone can show me the steps, it'll be greatly appreciated.

2 AnswersPhysics1 decade ago