@JohnRennie Hi :)

@KnightadmiresChappo hi :-)

@JohnRennie Aloha! (I have learned this new word)

Hawaian I believe ...

Hahahahaha yes

What you think of John Milton?

@KnightadmiresChappo I only read SF so I don't have any strong views about poets ...

@JohnRennie I'm searching for some purifying poem, I'm feeling very dirty from inside.

I can't help I'm afraid.

Can you help with EM waves? :)

Personally I deal with such issues by exercising e.g. go for a long walk or ccle ride.

Wow

@KnightadmiresChappo that's a complicated question that requires a knowledge of special relativity to answer it.

@JohnRennie really?

Yes.

My gosh they are asking it in an entrance exam for Undergrad admission

But I know a little of SR, so can we please do it sir?

In the lab rest frame the electric field is the sum of the two plane wave fields, and there is no magnetic field present. Yes?

@JohnRennie How can there be a wave without a B field?

OK, the B field is a factor of c smaller, so it is effectively zero.

okay

Now to find the force on the particle we need to transform into the rest frame of the particle i.e. we use a Lorentz transformation.

And the Lorentz transformation converts an electric field to a mixture of electric and magnetic fields.

So in the rest frame of the particle there are both an electric and a magnetic field present.

oh okay

I got it now.

So do the Lorentz transformation and you get new fields E' and B', then the force is F = q(E' + v x B')

Yes. Means it's just a problem of using the Lorentz Transformation, right?

Yes

Thank you so much sir :)

I can't remember the rules for transforming an electric field. You'll have to Google them.

I'm amazed that was asked for a university entrance exam.

Thats how my life is getting whacked sir

It's immoral to do that.

@JohnRennie

@CalvinKhor

Robbie sir

tomorrow is my exam, give me your precious blessings

Good luck!