Instead of the usual finding of potential difference across a component, in this question, you are required to find the p.d. across two points on the two separate branches. If you can relate the river system to the DC circuit, it will help in solving the last part. View the video tutorial

Do you understand why there is a potential difference between P and Q? What if you are to find the potential difference between P and Q? There is a shortcut to getting the answer for this MCQ, but watch the whole video to understand the concepts fully and find the value of the potential difference. Answer: Option D Video the explanation Another question with similar concept: 2012PPp2q07 https://www.sgphysicstuition.com/post/2012ppp2q07-find-the-p-d-across-a-and-c

Prefixes are used to denote very large or small physical quantities . It is important that you know all these prefixes well.

Light and sound are both waves. So both carry energy from one place to another. Light , which is part of the electromagnetic spectrum, is a transverse wave , It can travel through a vacuum at speed 3.0 x 108 m/s. As the light travels from an optically less dense medium (air) to an optically denser medium (liquid or glass) , the light undergoes refraction and bends towards the normal due to a decrease in speed . Light: Optically less dense medium to denser medium:  – speed decreases – wavelength shorter – frequency remains constant Sound is a longitudinal wave . It requires a medium to pass through and it cannot pass through a vacuum . Opposite to light, as the sound travels from a less dense medium (air) into a denser medium (water or solid) , the speed increases . Sound: Less dense medium to denser medium: – speed increases – wavelength longer – frequency remains constant Refers to the image below to understand how the waves behave in different mediums.

To do similar questions, it is important to know the 3 rays which have rules to follow in order to locate the image. Look through the video to learn the concepts and hopefully you can do similar questions in future.

The video include 3 different light experiments which involve glass block and pins. Most students faced difficulties in locating the pins through the glass block. It is important to close one eye and use your master eye to view. Hope this video helps! In experiments like this, the sources of error include: – the holes created by the pins are too big, hence the line drawn using the two holes may not be very precise, hence affecting the distance/angle measured (depends on experiments) – When putting back the glass block back on the paper, the position may be not exactly the same, hence affecting the angle/distance measured. As a precaution , it is good to ensure that the distance between the two pins are more than 4 – 5 cm. With the holes further apart, the line drawn will be more accurate.