Question
The photoelectric threshold wavelength for potassium (work function being 2eV ) is
|
(a) 310 nm |
(b) 620 nm |
(c) 1200 nm |
(d) 2100 nm |
✓
Answer
(b) 620 nm
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
The half life of polonium is 140 days. After how many days, 16 gm polonium will be reduced to 1 gm (or 15g will decay)
|
(a) 700 days |
(b) 280 days |
(c) 560 days |
(d) 420 days |
Electric current produced by a moving straight wire in a magnetic field is?
A cubical block of mass M and edge a slides down a rough inclined plane of inclination $\theta$ with a uniform velocity. The torque of the normal force on the block about its centre has a magnitude:
→-
$\text{Zero.}$
-
$\text{Mga}$
-
$\text{Mga}\sin\theta$
-
$\frac{1}{2}\text{Mga}\sin\theta$
Consider the situation of the previous problem. The directions of the magnetic field due to the dipole are opposite at:
A and B are two radioactive substances whose half lives are 1 and 2 years respectively. Initially 10 gm of A and 1 gm of B is taken. The time (approximate) after which they will have same quantity remaining is
|
(a) 6.62 years |
(b) 5 years |
(c) 3.2 years |
(d) 7 years |
An inductor, a resistance and a capacitor are joined in series with an AC source. As the frequency of the source is slightly increased from a very low value, the reactance:
- Of the inductor increases.
- Of the resistor increases.
- Of the capacitor increases.
- Of the circuit increases.
In the depletion region of a pn junction, there is a shortage of:
What is the equivalent capacitance between A and B in the given figure (all are in farad)
|
(a) |
(b) |
(c) |
(d) |
Which one of the following sentence is false?
A star emitting light of wavelength 5896 Å is moving away from the earth with a speed of 3600 km /sec. The wavelength of light observed on earth will (c = 3 
is the speed of light)
|
(a) Decrease by 5825.25 Å |
(b) Increase by 5966.75 Å |
|
(c) Decrease by 70.75 Å |
(d) Increase by 70.75 Å |