LEARNOGRAPHY

   What is the distance between two convex lenses L A  and L B  with focal lengths F A  and F B ? F A +F B F A -F B F A F B 2. If a medium has a critical angle for total internal reflection from the medium to vacuum as 30 0 , what is the velocity of light in the medium? 0.5 × 10 8  m/s 3 × 10 8  m/s 1.5 × 10 8  m/s 0.2 × 10 8  m/s 3. The combination of which of the following processes results in the formation of a rainbow? Dispersion and Total Internal Reflection Dispersion and Absorption Refraction and Scattering Dispersion and Focussing 4. What is the focal length of a double concave lens with a radius of curvature 20 cm, if the refractive index of the glass with respect to the air is 5/3? 20 cm -20 cm 15 cm -15 cm 5. A diverging lens of power 65 D is combined with a convex lens of focal length, f = 20 cm. What are the power and focal length of the combination? 5 D, 33.7 cm 5 D, 66.7 cm 1.5 D, 33.7 cm -1.5 D, 66.7 cm 6. When a thin convex l...

  1. Add a short note on Pyramid of biomass , energy and number . Ans:-         The relationship between numbers, biomass, energy or bio productivity of different trophic levels in an ecosystem can be represented by a pyramid known as the ecological pyramid or Eltonian pyramid. The ecological pyramids show the energy flow in the system . A biomass pyramid is the representation of total living biomass or organic matter present at different trophic levels in an ecosystem. Biomass is calculated as the mass of living organisms present at each trophic level in a given sample size. It can be represented as dry weight in grams or calories per unit area. A bomb calorimeter is used to measure biomass. Trophic level is the specific place that a living organism occupies in a food chain. In a biomass pyramid, producers (1 st  trophic level) are at the base, followed by herbivores (primary consumers) and then carnivores (secondary and tertiary consumers) at the top...

  Electric Charges and Fields Class 12 Notes Chapter 1 1. Electric Charge  Charge is the property associated with matter due to which it produces and experiences electric and magnetic effect. 2. Conductors and Insulators  Those substances which readily allow the passage of electricity through them are called conductors, e.g. metals, the earth and those substances which offer high resistance to the passage of electricity are called insulators, e.g. plastic rod and nylon. 3. Transference of electrons  is the cause of frictional electricity. 4. Additivity of Charges  Charges are scalars and they add up like real numbers. It means if a system consists of n charges q 1 , q 2 , q 3  , … ,q n , then total charge of the system will be q 1  +q 2  + … +q n . 5. Conservation of Charge  The total charge of an isolated system is always conserved, i.e. initial and final charge of the system will be same. 6. Quantisation of Charge  Charge exists in dis...