Я испугался, когда вдруг погас свет.

Испугался means got scared / became frightened. It describes a sudden change of state: at that moment, the speaker felt fear.

• испугался = got scared
• боялся = was afraid / feared (more like a state, not a sudden reaction)
• испугал = frightened someone; this is a different verb meaning scared as a transitive action

So Я испугался, когда вдруг погас свет means I got scared when the light suddenly went out, not I was generally afraid.

The base verb is испугаться. The ending -ся is part of the verb and often marks a reflexive or intransitive meaning.

Here, you should learn испугаться as a whole verb meaning to get frightened.

Compare:

• пугать = to frighten, to scare
• испугать = to frighten suddenly / to scare
• испугаться = to get frightened / to become scared

So Я испугался literally means something like I frightened myself only historically; in real usage, it simply means I got scared.

This is the past tense form.

In Russian past tense, verbs usually show:

• gender in the singular
• number
• but not person

So:

• я испугался = I got scared (male speaker)
• я испугалась = I got scared (female speaker)
• мы испугались = we got scared

The -л is the normal past-tense marker, and -ся is the reflexive ending.

It would be:

Я испугалась, когда вдруг погас свет.

Only испугался changes to испугалась.

That is because in the past tense, Russian singular verbs agree with the speaker’s gender:

• masculine: испугался
• feminine: испугалась
• neuter: испугалось (not used with я unless something non-human is speaking)

Когда means when.

It introduces a subordinate clause:

• Я испугался = I got scared
• когда вдруг погас свет = when the light suddenly went out

So the whole sentence is built like:

[main clause], [when-clause].

This is very similar to English.

Because Russian normally uses a comma to separate a main clause from a subordinate clause.

So in:

Я испугался, когда вдруг погас свет.

the comma marks the start of the when clause.

This is standard Russian punctuation, even where English might sometimes feel similar but not always identical.

Вдруг means suddenly or all of a sudden.

In this sentence it emphasizes that the light went out unexpectedly:

• когда вдруг погас свет = when the light suddenly went out

It often adds a feeling of surprise or abruptness.

Russian word order is flexible, and вдруг is often placed right before the verb to highlight the sudden event.

So:

• когда вдруг погас свет sounds natural and focuses on the suddenness of the action
• когда свет вдруг погас is also possible

Both are correct, but the rhythm and emphasis change a little.

Погас literally means went out or went dark/extinguished.

It is commonly used for:

• lights
• lamps
• candles
• flames
• anything that stops giving light

So погас свет = the light went out

This is close to выключился свет in some contexts, but погас sounds especially natural when talking about light disappearing, whether because of a power cut, a bulb failing, or the light simply going dark.

Because погас is intransitive here: the light itself went out.

• погас свет = the light went out
• я погасил свет = I turned off the light or literally I extinguished the light

So:

• погас = went out
• погасил = turned off / extinguished something

In your sentence, nobody is explicitly turning off the light; the light simply goes out.

Because свет is the subject of погас.

In other words:

• свет погас = the light went out
• свет is the thing performing the action grammatically

Even though in English we might think of this as something just happening, in Russian свет is still the subject, so it stays in the nominative case.

Both are possible.

• свет погас = more neutral, straightforward
• погас свет = often sounds a bit more narrative or dramatic, with focus on the event itself

Russian often puts the verb first to highlight what happened, especially in storytelling.

So когда вдруг погас свет feels vivid: when suddenly the light went out.

Yes, свет is singular.

But in Russian, свет often means:

• light
• the lighting
• electricity / power in context

So погас свет can naturally correspond to English:

• the light went out
• the lights went out
• sometimes even the power went out, depending on context

Russian uses singular свет very naturally in situations where English may prefer plural lights.

Both are perfective past-tense verbs.

That means they describe completed events:

• испугался = became scared at a particular moment
• погас = went out at a particular moment

This fits the sentence well, because it describes a sequence of sudden events:

1. the light went out
2. the speaker got scared

If you used imperfective forms, the meaning would change and sound less like a sudden one-time event.

For a general future idea, you could say:

Я испугаюсь, если вдруг погаснет свет.
I’ll get scared if the light suddenly goes out.

Notice the future perfective forms:

• испугаюсь
• погаснет

Russian often uses perfective verbs for single future events like this.

The verb испугаться usually takes the genitive case for the thing feared.

Examples:

• Я испугался шума. = I got scared because of the noise.
• Она испугалась темноты. = She got scared of the darkness.
• Мы испугались собаки. = We got scared of the dog.

In your sentence, the cause is expressed by the when-clause instead:

• Я испугался, когда вдруг погас свет.

So instead of saying I got scared of X, it says I got scared when Y happened.

A helpful stress guide is:

Я испуга́лся, когда́ вдруг пога́с свет.

Word by word:

• я
• испугался → stress on -га-
• когда → stress on final -да
• вдруг
• погас → stress on -гас
• свет

A rough pronunciation guide:

• Я = ya
• испугался = ee-spoo-GAL-sya
• когда = kag-DA
• вдруг = vdrook
• погас = pa-GAS
• свет = svyet

Yes, absolutely.

That version is also correct:

Когда вдруг погас свет, я испугался.

The meaning is the same. The difference is mostly one of emphasis:

• Я испугался, когда вдруг погас свет.
  Focuses first on I got scared
• Когда вдруг погас свет, я испугался.
  Sets the scene first: When the light suddenly went out...

Both are natural.