The permittivity of water at optical frequencies is $$1.75{\varepsilon _0}$$. It is found that an isotropic light source at a distance d under water forms an illuminated circular area of radius $$5m$$, as shown in the figure. The critical angle is $${\theta _c}$$

The value of $$d$$ (in meter) is ______ .

For a particular intensity of incident light on a silicon pn junction solar cell, the photocurrent density (J_L) is 2.5 mA/cm² and the open-circuit voltage (V$$_{oc}$$) is 0.451 V. consider thermal voltage (V$$_T$$) to be 25 mV. If the intensity of the incident light is increased by 20 times, assuming that the temperature remains unchanged. V$$_{oc}$$ (in volts) will be ______.

An npn bipolar junction transistor (BJT) is operating in the active region. If the reverse bias across the base-collector junction is increased, then

Consider the circuit shown in the figure. Assume base-to-emitter voltage V_BE=0.8 V and common base current gain $$\left(\alpha\right)$$ of the transistor is unity. The value of the collector-to–emitter voltage V_CE (in volt) is _______.