wǒ bú dài yǎnjìng jiù kànbuqīngchu hēibǎn shàng de hànzì.

Because of tone sandhi.

不 is normally fourth tone: bù. But when 不 comes before another fourth-tone syllable, it changes to second tone: bú.

• 不戴 → bú dài
• Compare:
  • 不是 → bú shì
  • 不高 → bù gāo (no change, because 高 is not fourth tone)

So in this sentence, 不戴 is pronounced bú dài because 戴 is fourth tone.

In Chinese, 戴 is the usual verb for things you wear on your head or on your body as accessories.

Common examples:

• 戴眼镜 = wear glasses
• 戴帽子 = wear a hat
• 戴手表 = wear a watch
• 戴口罩 = wear a mask

By contrast:

• 穿 is mainly for clothes: 穿衣服, 穿裤子
• 拿 means hold
• 用 means use

So 戴眼镜 is the natural expression for wear glasses.

戴 by itself is enough here.

着 often emphasizes a continuing state, like wearing something right now:

• 他戴着眼镜。 = He is wearing glasses.

But in this sentence, the speaker is talking about a condition:

• 我不戴眼镜就... = If I don’t wear glasses, then...

Because this is a general condition, 戴 sounds natural without 着.

You could sometimes hear 不戴眼镜 and 不戴着眼镜 in different contexts, but 不戴眼镜 is much more normal here.

Here 就 links the condition and the result. It is like then, in that case, or as soon as that happens.

Structure:

• A，就B
• If A, then B

So:

• 我不戴眼镜就看不清楚... = If I don’t wear glasses, then I can’t see clearly...

In English, then is often omitted, but in Chinese 就 is very common in this pattern.

Chinese often leaves out 如果 when the conditional meaning is already clear.

So both are correct:

• 我不戴眼镜就看不清楚黑板上的汉字。
• 如果我不戴眼镜，就看不清楚黑板上的汉字。

The version without 如果 is a little more direct and very natural in everyday speech.

No, they have different jobs.

1. 不戴眼镜

   • This 不 simply negates the verb 戴
   • 不戴眼镜 = not wear glasses

2. 看不清楚

   • This 不 is inside a verb-complement pattern
   • It shows failure or inability to achieve the result
   • 看不清楚 = cannot see clearly / fail to see clearly

So the first 不 is ordinary negation, while the second is part of the pattern verb + 不 + complement.

It is a very common Chinese pattern:

• 看 = look / see
• 清楚 = clear / clearly
• 看清楚 = see clearly
• 看不清楚 = not be able to see clearly

This is often called a potential complement or a verb + complement pattern.

Compare:

• 听得懂 = can understand by listening
• 听不懂 = can’t understand by listening
• 看得见 = can see
• 看不见 = can’t see

So 看不清楚 means that the action of seeing does not reach the result of clarity.

Yes, but the nuance is a little different.

• 看不清楚 = can’t see clearly / am unable to see clearly
• 看得不清楚 = see unclearly / do not see very clearly

In many situations they are close, but 看不清楚 is more natural here because the sentence is about inability caused by not wearing glasses.

So:

• 我不戴眼镜就看不清楚黑板上的汉字。 sounds very natural.

Literally, it is:

• 黑板 = blackboard
• 上 = on / on top of
• 的 = linking particle
• 汉字 = Chinese characters

So:

• 黑板上 = on the blackboard
• 黑板上的汉字 = the Chinese characters on the blackboard

This is a common modifier pattern in Chinese:

• [place + 上/里/下 + 的 + noun]

Examples:

• 桌子上的书 = the book(s) on the table
• 包里的手机 = the phone in the bag
• 墙上的画 = the painting on the wall

Because 黑板上 is modifying the noun 汉字.

In Chinese, when a phrase modifies a noun, 的 is often used to connect them:

• 黑板上的汉字 = the Chinese characters that are on the blackboard

Without 的, the phrase would sound incomplete or unnatural here.

So think of 的 as marking:

• the 汉字 belonging to / located on 黑板上

Chinese nouns usually do not change form for singular or plural.

So 眼镜 can mean:

• glasses
• a pair of glasses

The exact meaning comes from context.

If you want to count them, you can say:

• 一副眼镜 = one pair of glasses

But in a normal sentence like this, you just say:

• 戴眼镜 = wear glasses

That is the standard way.

汉字 is more specific: it means Chinese characters.

• 字 can mean character, word, writing, or handwriting depending on context.
• 汉字 clearly tells you the speaker means Chinese written characters.

So:

• 黑板上的汉字 = the Chinese characters on the blackboard

If you said 黑板上的字, it would also be understandable, but it would be less specific and could mean writing in general.

Yes, a little.

The original sentence is natural:

• 我不戴眼镜就看不清楚黑板上的汉字。

You could also say:

• 不戴眼镜，我就看不清楚黑板上的汉字。
• 如果我不戴眼镜，就看不清楚黑板上的汉字。

All of these work. The original version is smooth and conversational.

What you generally want to keep is this logic:

1. condition first
2. 就
3. result after that

So the core pattern is:

• (如果) A，就 B