Class 12th

Which one for the following phenols does not give colour when condensed with phthalic anhydride in presence of conc. H₂SO₄?

The interaction energy of London forces between two particles is proportional to r^x, where r is the distance between the particles. The value of x is:

The Major Product in the above reaction is :

For the given circuit, the power across zener diode is________mW.

A coil in the shape of an equilateral triangle of side 10cm lies in a vertical plane between the pole pieces of permanent magnet producing a horizontal magnetic field 20mT. The troque acting on the coil when a current of 0.2A is passes through it and its plane becomes parallel to the magnetic field will be $\sqrt[]{x}*10^{-5}$ Nm. The value of x is_________.

A circular coil of radius 8.0cm and 20 turns is rotated about its vertical diameter with an angular speed of 50 rad s^-1 in a uniform horizontal magnetic field at 3.0 * 10^-2 T. The maximum emf induced in the coil will be________* 10^-2 volt (rounded off to the nearest integer).

An amplitude modulated wave is represented by   $C_m\left(t\right)=10\left(1+0.2cos12560t\right)sin\left(111*10^{4}t\right)volts.$

The modulating frequency in kHz will be……. .

The electric field in a plane electromagnetic wave is given by

$\overrightarrow{E}=200cos\left[\left(\frac{0.5*10^3}{m}\right)x\left(1.5*10^{11}\frac{rad}{s}*t\right)\right]\frac{V}{m}\widehat{j}$

If this wave falls normally on a perfectly reflecting surface having an area of 100 cm². If the radiation pressure exerted by the E.M. wave on the surface during a 10 minute exposure is $\frac{x}{10^9}\frac{N}{m^2}.$   Find the value of x

An object is placed at a distance of 12 cm from a convex lens. A convex mirror of focal length 15 cm is placed on other side of lens at 8cm as shown in the figure. Image of object. When the convex mirror is removed, a real and inverted image is formed at a position. The distance of the image from the object will be________ (cm).

White light is passed through a double slit and interference is observed on a screen 1.5m away. The separation between the slits is 0.3mm. The first violet and red fringes are formed 2.0mm and 3.5mm away from the central white fringes. The difference in wavelengths of red and violet light is………nm.