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1. Questions on vectors

I just learnt vectors as a prerequisite to learning mechanics and I have a few doubts:- 1) For 1D motion, there are only two possible directions, so they can be represented by just a + or - sign, where you have to define which direction is positive and which is negative. But for 2D how do...
2. Image formation at infinity

In astronomical telescopes, they use a convex mirror to from a real image, which is formed at the focus of the eyepiece lens, effectively forming an image at infinity. But how can it truly be at infinity? If it was truly at infinity then how could you see it? Also they say that image at infinity...
3. Why are clouds white?

In one place I read that since the particles are big they reflect white light as is. But in another I read that they are made up of water droplets of varying sizes so, small droplets: make blue medium droplets: make green larger droplets: make red ...and together they combine to make a white...
4. Functioning of a compound microscope

"The diameter of the eyepiece is greater than that of the objective. This helps to collect more light and gives a brighter image" I thought that increasing the aperture of a lens doesn't increase the brightness of a virtual image. Yes, it will increase the brightness of a real image caught on...
5. Magnification of an image

We're learning about magnification and they say how magnification is the ratio of the visual angle while looking through the instrument to that with the naked eye and then they say, For small angles, magnification is defined as, m= height of the image/height of the object Why only for...
6. The sky's red color during sunset and sunrise

I understand why the sun is red,, due to most of the blue light of shorter wavelength being scattered in other directions because the sunlight has to travel through more atmosphere before it reaches our eyes, but why does the surrounding sky appear red to us?
7. Does dispersion of light occur in reflection?

During refraction the different colors that white light is composed of are dispersed but does this happen during reflection or total internal reflection?
8. Formation of spectrum of colors when light passes through a flat pane of glass

Here's a question from my textbook: "Why do you not see a spectrum of colors when light passes through a flat pane of glass?" However I think that a spectrum of colors will be formed when light passes through a flat pane of glass. The colors will all be parallel to one another, unlike a prism...
9. Refraction (aperture, apparent depth)

Homework Statement 1: A decrease in the aperture of a lens changes the (A)Size of the image (B)Intensity of the image (C)Portion of the image (D) All of these 2: A vessel is filled with two different liquids which do not mix. One liquid is 40cm deep and has n=1.6 and the other is 30cm deep...
10. Wider viewing angles

There's a para in my textbook which doesn't make much sense to me: An observer or a fish under water looks up to see a compressed view of the outside world. The 180 degree view from horizon to horizon is seen through an angle of 96 degrees (twice the critical angle). A lens, called fish eye...
11. Refraction - A fish under water

Refraction -- A fish under water Homework Statement 1 A fish under water obliquely sees a fisher-man standing on the bank of a lake. How does he appear? 2 A parallel sided glass plate is introduced in the path of a converging beam. What happens to the point of convergence of the beam...
12. Lens and Mirror formula

So we are learning the lens formula and I have two textbooks, my school textbook and another one that is much more detailed. My school textbook gives the lens formula as:- 1/f=1/v-1/u while the other one gives 1/f=1/v+1/u (v is image distance and u is object distance) There both different! I...
13. Refraction: Reflection after passing the critical angle

If the angle of incidence is greater than the critical angle then it is reflected back in to same medium. Is this reflection normal reflection? (as in it obeys all the rules of reflection, like reflection in mirrors) Or is it a bit different?
14. Convex lenes

I'd like to know why a ray of light passing through the optical center of a convex lens does not get refracted at all. According to my knowledge, a ray of light will not get refracted if the angle of incidence is zero i.e. it is along the normal. With this in mind, I see how a ray travelling...
15. Image formation in concave mirrors

When you look in spoon from a reasonable distance you see an inverted image of yourself in the mirror. How can you see a real image in the mirror when I thought you saw virtual images in a mirror and real images had to be caught on a screen.
16. Mirrors and images

Homework Statement The rear view mirror of a car is a plane mirror. A driver is reversing his car at the speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind hid car. The speed at which the image of the truck appears to approach the driver will be? The...
17. Lateral inversion up-left and down-right confusion

Hi :) So I'm learning about lateral inversion in plane mirrors and it's a bit confusing. I think of it like this:- Suppose you had a clone of your self who is standing next to you and facing the same direction. He walks a few steps forward and then turns to face you. When he turns to face...
18. Reflection in spherical mirrors

Hey everyone, I'm reading a chapter on reflection of Light and I had some doubts:- 1 Is a real, erect image possible? What about a virtual, inverted image? 2 How can you see a real image without a screen? Can you see it in the air or something? 3 When you move away from a plane mirror...
19. Contradicting conclusions on falling bodies.

I was recently thinking about potential energy and I came to two conclusions which contradict each other- 1)When a body is falling from a height, the force of gravity is acting on it in the downwards direction. There is displacement in the downwards direction. So as the force and the...
20. Spring balances

Q. A spring balance read 10 kg when a bucket of water is suspended from it. An iron piece having some mass is suspended by another string and is then immersed in the bucket with half of its volume. The reading of the spring balance will - (A)decrease (B)increase (C)remain the same...
21. Mechanical waves compressions and rarefactions

Are all mechanical waves composed of compressions and rarefactions ? Apart from sound waves what other mechanical waves are there ?
22. Doubts on longitudinal waves

In my text book they have introduced the concept of longitudinal waves and go on to explain what a compression and what a rarefaction is.It is written- "In a compression, there is a temporary increase in the density of the medium; and in a rarefaction,there is a temporary decrease in the...
23. Questions on buoyancy

1)How can a fluid exert pressure in all directions ?The only force that a fluid exerts is its weight (as far as I know) and as weight acts downwards, fluids should only exert pressure in the downward direction. Also why do they say fluids exert pressure in all directions ? Why can't they say...
24. Sqrt (-1) * sqrt (-1)

sqrt(A)*sqrt(B)=sqrt(A*B) Therefore, sqrt(-1)*sqrt(-1)=sqrt(-1*-1) =sqrt(1) =1 This doesn't make sense.Did I do something wrong ?
25. Doubts regarding Atomic mass,relative atomic mass and mass number.

I was reading my science textbook and they have introduced the concepts of atomic mass,relative atomic mass and mass number.Here are some doubts I have- 1)Is atomic mass a ratio ? 2)1/12th of a C-12 atom is half a proton,half a neutron and half an electron.Since mass of an electron is...
26. Measurement problem involving scale

A rectangular park has an area of five hectares (1 hectare = 10,000 meter square) The dimensions of the park on a map are 5 cm * 4 cm What is the scale of the map?
27. A few questions on various topics

Here are a few doubts that I had while reading for an upcoming exam.While answering please keep in mind that I'm in 9th grade so simple answers would be better- 1)Why is the electronic configuration of Chromium - [Ar] 3d5 4s1 instead of [Ar] 3d4 4s2 ? Similarly why does Coppers electronic...
28. What is a constant

Could someone please explain the concept of a constant in simple terms?
29. Question on work and energy

These are some of my question related to work and energy- 1)W is proportional to Force W is proportional to displacement Therefore, W=Fs My question is why do we have to multiply F and s.Why can't we add them.Why can't the formula be W=F+s 2)In space if you were to push an object it...
30. Question on conservation of momentum

When you jump on a weighing scale the instant that you hit you're weight is higher than it would be if you were to gently step on on.Can someone give me a proper answer? I think its somehow related to conservation of momentum but i cant think of a proper answer. Also,suppose you two balls and...