714 views

### Light and momentum question? [duplicate]

Each photon of light bulb carries momentum. Why does the light bulb not recoil from conservation of momentum?
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### Does third law of motion apply to light or EM waves? [duplicate]

Third law of motion - "For every action there is an equal and opposite reaction" I was considering the situation, where I may be motionless in space with only a flashlight and no forces acting on me. ...
• 569
1 vote
689 views

### Calculating the force imparted on an object by a laser [duplicate]

It has recently been mooted that micro-satellites could be propelled to nearby stars through the use of powerful, ground based laser systems. However, given that light has no mass, I don't know how to ...
1 vote
347 views

### Momentum of Light Question [duplicate]

Since light beams carry momentum, why would a person holding a flashlight not feel a recoil similar to that of a rifle being fired?
122 views

### Does light (photons) exert reaction force on it's source? [duplicate]

I know that photons/ light when incident on a surface exerts forces on it (aka radiation pressure) and it is also used for applications such as solar sails or laser propulsion. This phenomenon is ...
57 views

### Do EM waves carry momentum and if they do can it be used to generate thrust? [duplicate]

I read EM waves carry momentum and can exert pressure, if this is the case can ejecting them be used to generate thrust? Radiation pressure is cited as a real thing but I read about the EM drive and ...
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1 vote
66 views

### Can I close my door with a torch? [duplicate]

Photon pressure is definitely one of the most amazing phenomenon that I have heard in a while. Some examples: The pressure from the photons emitted by the Sun can perturb the motion of artificial ...
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1 vote
56 views

### Will the flash light accelerate in space? [duplicate]

As we know from school physics course light has pressure. So my question is will flash light accelerate in space in the direction opposite to light emission? If not, then will flash light with ...
51 views

### How come $P=Fv$ applies to light? [duplicate]

I was asked the following question in a physics worksheet: A $2.0 \,\mathrm{mW}$ laser is shone onto a metal plate. The cross-sectional area of the beam is $4.0\times 10^{-6} \, \mathrm m^2$. Assume ...
263k views

### If photons have no mass, how can they have momentum?

As an explanation of why a large gravitational field (such as a black hole) can bend light, I have heard that light has momentum. This is given as a solution to the problem of only massive objects ...
• 2,746
1 vote
738 views

### Does light have mass? [closed]

Does light have mass? If yes, will it exert force? If no, then how are light particles are travelling at light speed? If light doesn't have mass how is it attracted by gravitational force (black holes)...
• 31
709 views

### Force acting on particles/waves

I know from quantum mechanics that any matter particle has both wave and particle properties. So my question is that like in Newtonian mechanics we calculate the force acting on a particle by ...
• 262
212 views

### Can acceleration be achieved without reaction mass?

In a previous question, I asked whether a flashlight can accelerate me. The answer is yes. This has led me to wonder, this is inferior to all other known propulsion methods in all aspects except one: ...
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1 vote
164 views

### Is radiation pressure wavelength dependent (does a blue photon move the solar sail more then a red photon)?

I have read this question: Where John Rennie says: Does the wavelength of the light matter? No Now in the same question, another answer, by DavePhd says: Does the wavelength of the light matter? ...
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