OCR Gateway Physics P4P5P6 - 18/06/13

In the exam, are we allowed to use a pencil to draw diagrams, because I don't think it says so on the front? :smile:

Reply 342

Original post by BP_Tranquility

In the exam, are we allowed to use a pencil to draw diagrams, because I don't think it says so on the front? :smile:

Yes - and graphs

Reply 343

BrokenS0ulz

3

For the relay circuit symbol, which one do we have to learn? There is loads of different symbols for a relay

Reply 344

AcuraIntergurl

Does anyone understand Optics?

Reply 345

I'm finding 'images' really hard to get my head around :frown:

Reply 346

Knowing

1

Could someone explain interference please? The bit where you have two coherent wave sources and you need to know where there is a destructive or a constructive interference pattern.

Reply 347

Mathangi

9

I think I understand the equations from points one to four, but I don't understand how they relate to points five and six?

Where is the force coming form? I'm really confused?

Reply 348

Original post by cameron262

I think I understand the equations from points one to four, but I don't understand how they relate to points five and six?

Where is the force coming form? I'm really confused?

When the gas particles collide with the walls or the container, their momentum changes because they slow down. The momentum is conserved because a bit of the particle's momentum goes into pushing the wall a bit, so a force is exerted on the wall. This happens loads of times and in loads of different places. This is pressure.

The equations are just proving why the gas particles cause there to be pressure.

Reply 349

NatashaG

11

Original post by Knowing

Could someone explain interference please? The bit where you have two coherent wave sources and you need to know where there is a destructive or a constructive interference pattern.

You have a constructive interference with areas of bright light (using light source) or loud areas (using sound waves) and destructive interference pattern are areas of no light or quiet areas

Reply 350

Original post by cameron262

I think I understand the equations from points one to four, but I don't understand how they relate to points five and six?

Where is the force coming form? I'm really confused?

When particles are moving they have momentum, so when they hit the walls of the container, that momentum changes, as the particles rebound off of it. When the particles collide with the wall, this creates a force on the walls, because the particles have hit the walls (just like how if you hit a tennis ball with a racket, you're creating a force on the ball so it moves).

The force created by the particles against the walls, also generates pressure (force is measured in Newtons whilst pressure is measured in Newtons per metre squared, so they are very similar but pressure is more specific as it tells you how much force is acting per a certain amount of area whilst force is 'general' and not as specific).

The pressure on the walls can be changed, which is what point 6 is referring to. By increasing the temperature, the particles inside the container have more kinetic energy so they collide more frequently and more violently against the walls of the container, which in turn creates a larger pressure being exerted on the walls. You can also increase the pressure on the walls by reducing the amount of volume inside the container- e.g. if you halve the amount of volume/space inside the container, then the particles are closer together so they are more likely to collide against the walls because there's less space for them to move about in. :smile:

Reply 351

Original post by andersson

I'm finding 'images' really hard to get my head around :frown:

What do you struggle with? :smile:

If you mean the virtual/real images, then all we have to know is the difference between them- virtual cannot be projected and is the right way up whilst real images can be projected and the image is inverted... :cool:

Reply 352

Original post by Knowing

Could someone explain interference please? The bit where you have two coherent wave sources and you need to know where there is a destructive or a constructive interference pattern.

Think of it in terms of path difference (basically the distance the two waves have traveled relative to each other):

If the waves have a path difference of a whole number of wavelengths (e.g. 1λ, 2λs, 5λs or 47247392λs) then the crests of the wave line up when they meet each other. They're both trying to cause a disturbance in the same direction so the wavelengths join and form one wave with an increased amplitude (this is constructive interference).

If the waves have a path difference with half a wavelength (e.g. 1.5λs, 3.5λs, 43.5λs) the crests and the troughs line up. The waves are tying to cause a disturbance in opposite directions so when the wavelengths meet there is no disturbance (there's just a line). This is destructive interference.

With light, constructive interference shows a light spot. Destructive interference shows a dark spot (because the waves have cancelled each other out).

Hope that helps! (It helped me trying to explain it :tongue:

)

Reply 353

Original post by BP_Tranquility

What do you struggle with? :smile:

If you mean the virtual/real images, then all we have to know is the difference between them- virtual cannot be projected and is the right way up whilst real images can be projected and the image is inverted... :cool:

Yeah that makes sense, cheers. It's just GCSE over-simplification of quite an abstract topic, so I was trying to understand it fully when we only need to know it on a really simple level :lol:

Reply 354

Original post by andersson

Yeah that makes sense, cheers. It's just GCSE over-simplification of quite an abstract topic, so I was trying to understand it fully when we only need to know it on a really simple level :lol:

GCSE oversimplification sometimes makes things more complicated, since you don't fully understand it (just like how I found metallic bonding confusing at first because we weren't, and still haven't, been taught why it happens), so you're not alone :tongue:

Reply 355

Knowing

1

Original post by NatashaG

You have a constructive interference with areas of bright light (using light source) or loud areas (using sound waves) and destructive interference pattern are areas of no light or quiet areas

Original post by andersson

Think of it in terms of path difference (basically the distance the two waves have traveled relative to each other):

If the waves have a path difference of a whole number of wavelengths (e.g. 1λ, 2λs, 5λs or 47247392λs) then the crests of the wave line up when they meet each other. They're both trying to cause a disturbance in the same direction so the wavelengths join and form one wave with an increased amplitude (this is constructive interference).

If the waves have a path difference with half a wavelength (e.g. 1.5λs, 3.5λs, 43.5λs) the crests and the troughs line up. The waves are tying to cause a disturbance in opposite directions so when the wavelengths meet there is no disturbance (there's just a line). This is destructive interference.

With light, constructive interference shows a light spot. Destructive interference shows a dark spot (because the waves have cancelled each other out).

Hope that helps! (It helped me trying to explain it :tongue:

)

Thanks you two :smile:

got it now :biggrin:

Reply 356

Original post by BP_Tranquility

GCSE oversimplification sometimes makes things more complicated, since you don't fully understand it (just like how I found metallic bonding confusing at first because we weren't, and still haven't, been taught why it happens), so you're not alone :tongue:

Yup! And sometimes in the exam I have to stop myself from going into too much detail because I remind myself that it's just GCSE :biggrin:

Reply 357

Original post by Knowing

Thanks you two :smile:

got it now :biggrin:

But mainly thanks to me :wink:

Reply 358