Question
Two thin lenses whose powers are +2D and –4D respectively combine, then the power of combination is(a) – 2D(b) + 2D(c) – 4D (d) + 4D
✓
Answer
(a) – 2D
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
Internal resistance of the cell is:
Assertion : When the speed of an electron increases its specific charge decreases.
Reason : Specific charge is the ratio of the charge to mass.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.
Reason : Specific charge is the ratio of the charge to mass.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.
In an electron gun, the electrons are accelerated by the potential $V .$ If $e$ is the charge and $m$ is the mass of an electron, then the maximum velocity of these electrons will be
→When a charged body is brought near an electroscope:
Assertion : The following circuit represents $'OR\ '$ gate
Reason : For the above circuit $Y=\bar{X}=\overline{\overline{A+B}}=A+B$
→Reason : For the above circuit $Y=\bar{X}=\overline{\overline{A+B}}=A+B$
The PN junction diode is used as(a) An amplifier(b) A rectifier(c) An oscillator(d) A modulator
In the given figure, battery $E$ is balanced on $55 \ cm$ length of potentiometer wire but when a resistance of $10\Omega$ is connected in parallel with the battery then it balances on $50 \ cm$ length of the potentiometer wire then internal resistance $r$ of the battery is
→The value of electric potential of a distance $r$ from a point charge $q$ is :
→It is desired to photograph the image of an object placed at a distance of 3m from the plane mirror. The camera which is at a distance of 4.5 m from the mirror should be focussed for a distance of(a) 3m(b) 4.5m(c) 6m(d) 7.5 m
When a hydrogen bomb explodes, which of the following is used?