Basics of Physics

  Qu. The amount of force exerted on a unit positive charge in an electric field is known as... a) Electric field intensity b) Electric flux c) Electric potential d) Electric lines of force Answer: The amount of force exerted on a unit positive charge in an electric field is known as  Electric field intensity.

  Qu.  Is the image on a movie screen real or virtual? How do we know? Answer: The projector in the cinema uses a reel on which light is incident and passes through it instead of getting reflected. The light which passes through it makes the geometrical shadows of the objects which are there on the reel.  From the above explanation it is very clear that the image that we see on a movie screen is a real image. 

  Qu. How many Balmer series lines are in the visible part of the spectrum? Answer: The Balmer series or Balmer Lines are one of the sets of six named series which describe the spectral line emission of the hydrogen atom. The Balmer series is characterized by the electron making the transition from  n ≥ 3   t o   n = 2 . Where n is principal quantum number of the electron. The visible spectrum of light from hydrogen displays 4 wavelengths, 410 nm, 434 nm, 486 nm, and 656 nm. These wavelengths are corresponding to the emission of photons by electrons in excited making the transition to the quantum level having principal quantum number n=2. Therefore, 4 Balmer series lines are in the visible part of the spectrum.

 Qu. Answer: Applying Kirchhoff's loop law in the above circuit, we get, Answer: